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Báo cáo Y học: Purification and characterization of novel chondroitin ABC and AC lyases from Bacteroides stercoris HJ-15, a human intestinal anaerobic bacterium pptx

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The purified Bacteroidal chondroitin ABC lyase acted to the greatest extent on chondroitin sulfate A chondroitin 4-sul-fate, to a lesser extent on chondroitin sulfate B dermatan sulfate a

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Purification and characterization of novel chondroitin ABC and AC

bacterium

Sung-Woon Hong1, Byung-Taek Kim1, Ho-Young Shin1, Wan-Suk Kim2, Keun-Sook Lee1, Yeong-Shik Kim2 and Dong-Hyun Kim1

1

College of Pharmacy, Kyung Hee University, Seoul, Korea;2Natural Products Research Institute, Seoul National University, Seoul, Korea

Two novel chondroitinases, chondroitin ABC lyase

(EC 4.2.2.4) and chondroitin AC lyase (EC 4.2.2.5), have

been purified from Bacteroides stercoris HJ-15, which was

isolated from human intestinal bacteria with

glycosami-noglycan degrading enzymes Chondroitin ABC lyase was

purified to apparent homogeneity by a combination of

QAE-cellulose, CM-Sephadex C-50, hydroxyapatite and

Sephacryl S-300 column chromatography with a final

spe-cific activity of 45.7 lmolÆmin)1Æmg)1 Chondroitin AC

lyase was purified to apparent homogeneity by a

combina-tion of QAE-cellulose, CM-Sephadex C-50, hydroxyapatite

and phosphocellulose column chromatography with a final

specific activity of 57.03 lmolÆmin)1Æmg)1 Chondroitin

ABC lyase is a single subunit of 116 kDa by SDS/PAGE and

gel filtration Chondroitin AC lyase is composed of two

identical subunits of 84 kDa by SDS/PAGE and gel

filtra-tion Chondroitin ABC and AC lyases showed optimal

activity at pH 7.0 and 40C, and 5.7–6.0 and 45–50 C, respectively Both chondroitin lyases were potently inhibited

by Cu2+, Zn2+, and p-chloromercuriphenyl sulfonic acid The purified Bacteroidal chondroitin ABC lyase acted to the greatest extent on chondroitin sulfate A (chondroitin 4-sul-fate), to a lesser extent on chondroitin sulfate B (dermatan sulfate) and C (chondroitin 6-sulfate) The purified chon-droitin AC lyase acted to the greatest extent on chonchon-droitin sulfate A, and to a lesser extent on chondroitin C and hyaluronic acid They did not act on heparin and heparan sulfate These findings suggest that the biochemical proper-ties of these purified chondroitin lyases are different from those of the previously purified chondroitin lyases

Keywords: Bacteroides sterocirs HJ-15; chondroitin ABC lyase; chondroitin AC lyase; chondroitin sulfate; purifica-tion

Enzymes degrading glycosaminoglycans (GAGs) have been

become increasingly important in understanding of the

GAGs and proteoglycans, which are involved in the

regulation of various cellular processes such as adhesion,

differentiation, migration and proliferation [1–5] The

design and preparation of GAG-based therapeutic agents

becomes possible using these enzymes [6] Chondroitin

sulfates are the most common type of GAG chains found in

proteoglycans [6,7] They are sulfated linear polysaccharides

with alternating 1–3 and 1–4 linkages The major classes are

chondroitin sulfate A, dermatan sulfate (chondroitin

sul-fate B) and chondroitin sulsul-fate C The biological roles of

chondroitin sulfate GAGs are poorly understood and their

exact chemical structures have not been determined

Enzyme methods are preferable to chemical methods when

determining polysaccharide structures [8,9] Enzymes are

often very specific and act under mild conditions giving oligosaccharide products Two classes of enzyme that act on GAGs are polysaccharide lyases and hydrolases Prokar-yotic polysaccharide lyases depolymerize GAGs through an eliminative mechanism, whereas enzymes from eukaryotic sources act through a hydrolytic mechanism [6]

Bacterial degradation of GAGs has been studied using enzymes produced from Flavobacterium heparinum [10–13] and Bacteroides thetaiotaomicron [14,15] Recently, the acharan sulfate degrading bacterium was isolated from human intestine and identified as Bacteroides stercoris HJ-15 [16] This organism also cleaved heparin, heparan sulfate, chondroitin sulfate A, chondroitin sulfate C and even dermatan sulfate [16–18]

We report here reproducible schemes for the purification

of chondroitin ABC lyase and chondroitin AC lyase, which have not been purified from Bacteroides sp., to apparent homogeneity and the determination of their physical properties, kinetic properties, optimal catalytic conditions and specificity

M A T E R I A L S A N D M E T H O D S

Materials Chondroitin sulfate A (chondroitin 4-sulfate from bovine trachea), chondroitin sulfate B (dermatan sulfate from bovine mucosa), chondroitin sulfate C (chondroitin

Correspondence to D.-H Kim, College of Pharmacy,

Kyung Hee University, 1, Hoegi-dong, Dongdaemun-ku,

Seoul 130-701, South Korea.

Fax: + 82 2 957 5030, Tel.: + 82 2 961 0374,

E-mail: dhkim@khu.ac.kr

Abbreviations: GAG, glycosaminoglycan; IEF, isoelectric focusing.

Enzymes: chondroitin ABC lyase (EC 4.2.2.4); chondroitin AC lyase

(EC 4.2.2.5).

(Received 22 January 2002, revised 23 April 2002,

accepted 30 April 2002)

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6-sulfate from shark cartilage), hyaluronic acid (rooster

coomb), heparin (porcine intestinal mucosa), porcine

heparan sulfate (porcine intestinal mucosa), thioglycolic

acid (sodium salt), QAE-cellulose fastflow, HA Ultrogel

(microcrystalline hydroxyapatite, 4% beaded in agarose),

phosphocellulose (coarse mesh) and low molecular mass

markers for gel filtration were purchased from Sigma

Chemical Co CM-Sephadex C-50, Sephacryl S-300 HR

resins, high molecular mass markers for gel-filtration and

low molecular mass markers for protein electrophoresis

were from Amersham Pharmacia Biotech DEAE-cellulose

resin was obtained from Wako Pure Chemical Industries

Protein Assay Reagent, SDS and Coomassie Brilliant Blue

R-250 were supplied by Bio-Rad laboratories Tryptic soy

broth was provided by Difco Co Acharan sulfate, which

has a uniform repeating disaccharide structure of fi

4)-a-D-GlcNAc(1fi 4)-a-L-IdoA2S(1fi , was prepared from

the giant African snail, Achatina fulica, according to the

previous method [17] All other chemicals were of the

highest grade available

Bacterial strains and cultivation

B stercorisHJ-15 was isolated and cultivated as described

previously [16] It was cultured anaerobically under an

atomosphere of 90% nitrogen and 10% carbon dioxide at

37C in 10 L of tryptic soy broth (pH 7.2) containing

chondroitin sulfate A (0.15 gÆL)1) instead of glucose,

0.01% (w/v) sodium thioglycolate and 0.1% (w/v)

ascorbic acid

Purification procedure of chondroitin ABC lyase

The cultured cells in 10-L of the broth described above were

harvested in the late exponential phase (11–12 h) by

centrifugation at 3000 g for 30 min at 4C and the resulting

cell pellet was washed twice with cold 0.89% NaCl The cell

pellet was suspended in 150 mL of 50 mM sodium

phos-phate buffer, pH 7.0 Cell suspension (30 mL at a time) was

placed into a 50-mL centrifuge tube and disrupted by

15-min periods of sonication at 1-s intervals on an ultrasonic

processor (Eyela Co.) at a 40% output with cooling Cell

debris was removed by centrifugation at 21 000 g for

60 min at 4C All operations were carried out at 4 C

unless otherwise noted One hundred and fifty milliliters of

cell extract (or 150 mL) was passed through a

QAE-cellulose column (2.8· 38 cm) which had been

preequili-brated with 200 mL of 50 mM sodium phosphate buffer,

pH 7.0 The column was washed with the same buffer until

no further lyase activities were detectable in the effluent The

noninteracting fluid (350 mL) passed through the column

and was loaded onto a CM-Sephadex C-50 column

(2.8· 38 cm) equilibrated with 50 mM sodium phosphate

buffer, pH 7.0 and the column was washed with 300 mL of

the same buffer (the fraction passing through the column

without binding was used for the purification of chondroitin

AC lyase) Then CM-Sephadex C-50 column binding

chondroitin ABC lyase was eluted with a total 300 mL

linear gradient of KCl from 0 to 0.6M in 50 mM sodium

phosphate buffer, pH 7.0 (Fig 1) The fractions containing

chondroitin ABC lyase activity were pooled and dialyzed

against 3 L of 50 mMsodium phosphate buffer, pH 7.0 for

12 h for next step The dialyzed enzyme preparation was

applied to a hydroxyapatite column (2.5· 6 cm) previously equilibrated with 50 mMsodium phosphate buffer, pH 7.0 The column was washed with 500 mL of the same 50 mM sodium phosphate buffer, pH 7.0 and then eluted with an 800-mL linear gradient of potassium chloride from 0 to 0.5M Chondroitin lyase-positive fractions were pooled and concentrated to approximately 2 mL by a ultrafiltration unit (Advantec Co.) The concentrated enzyme preparation was loaded onto a Sephacryl S-300 HR column (3.5· 70 cm) and eluted with 50 mM sodium phosphate buffer, pH 7.0 at a flow rate of 1 mLÆmin)1 Fractions containing chondroitin ABC lyase activity were tested for purity by electrophoresis

Purification procedure of chondroitin AC lyase fromB stercoris HJ-15

In the procedure of the purification of chondroitin ABC lyase, the fluid (390 mL) passing through CM-Sephadex C-50 column (2.8· 38 cm) without binding was pooled and its activity was measured (Fig 1) The crude chondroitinase

AC lyase was applied to a hydroxyapatite column (3· 10 cm) previously equilibrated with 50 mM sodium phosphate buffer, pH 7.0 The column was washed with

500 mL of the same 50 mM sodium phosphate buffer,

pH 7.0 and then eluted with a total 800 mL linear gradient

of potassium chloride from 0 to 0.5M Chondroitin AC lyase-positive fractions were pooled and dialyzed against

3 L of the same buffer The desalted enzyme preparation was loaded onto a phosphocellulose column (3· 10 cm) preequilibrated with 50 mM sodium phosphate buffer,

pH 7.0 and unbound proteins were removed by a 500-mL wash of 50 mM sodium phosphate buffer, pH 7.0 The column was eluted with total 400 mL linear gradient of 50–

400 mM sodium phosphate and chondroitin AC lyase activity containing fractions were tested for homogeneity

by electrophoresis

Enzyme activity assays Chondroitin lyase activity was measured according to the following method The spectrophotometer (Jasco V-530) was adjusted to 40C and a 1-mL quartz cuvette containing

Fig 1 Elution profile of chondroitin lyases on CM-Sephadex C-50ion exchange chromatography Solid circle, chondroitin sulfate A-degra-ding activity; open circle, dermatan sulfate-degraA-degra-ding activity; solid triangle, chondroitin sulfate C-degrading activity; simple line, absorbance at 280 nm.

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1 mg of substrate in 650 lL of 50 mM sodium acetate

buffer, pH 5.8 for chondrotinase AC (or 50 mM sodium

phosphate buffer, pH 7.0 for chondroitinase ABC) was

thermally equilibrated Fifty microliters of enzyme solution

was added and the cuvette was gently inverted twice to mix

the contents It was then immediately placed in the warmed

holder of spectrophotometer and the change of absorbance

at 232 nm was measured at 1-s intervals over 5 min The

activity was calculated from the change of absorbance per

minute using an extinction coefficient of 3800M )1 for

products (1 U¼ 1 lmol of uronic acid containing product

formed per min) [19] The specific activity was calculated by

dividing the micromoles of product produced per minute by

the milligrams of protein in the cuvette

Protein determination

Protein concentration was measured by a Bradford assay

based on a bovine serum albumin standard curve [20]

Characterization of chondroitin lyases

SDS/PAGE was performed for the determination of

molecular mass according to Laemmli’s procedure [21]

The gels were stained with Coomassie Brilliant Blue

R-250 solution and further stained with silver The pI

values of chondroitin lyases were determined by IEF

electrophoresis using Model 111 Mini IEF Cell (Bio-Rad)

according to the manufacturer’s instructions The

molecu-lar mass of the native enzyme was estimated by

gel-filtration using Sephacryl S-300 HR column (1.6· 70 cm)

calibrated with gel filtration low molecular mass

calibra-tion kit (from Sigma Co.) and high molecular calibracalibra-tion

kit (from Amersham Pharmacia Biotech) The pH

opti-mum of chondroitin lyases were determined using 50 mM

sodium phosphate buffer (pH 5.0–8.5) The temperature

dependence of the enzyme was investigated by measuring

enzyme activity at different temperatures (20–60C) To

investigate the effect of divalent metal ions and KCl on

the lyase activity, divalent metal ion (final concentration,

100 lM) and KCl (0–500 mM) were added into the

reaction mixture (acetate buffer was used instead of

phosphate buffer) Kinetic constants of chondrotin lyases

were determined by measuring the initial rates at various

substrate concentrations (200, 400, 600, 1000, 2000,

3000 lg) under the standard reaction conditions These lyase activities on other sulfated polysaccharides were also measured One milligram of each substrate was added to the reaction mixture

Amino-acid composition analysis was performed on an Applied Biosystem model 420/130 Derivatizer/Amino Acid Analyzer, using phenylisothiocyanate precolumn derivati-zation chemistry Hydrolysis was performed using using 6M hydrochloric acid, 0.1% phenol at 155C for 1 h

Internal amino-acid sequences of two purified chondro-itin lyases were analyzed by an Applied Biosystem protein sequencer model 492

R E S U L T S

Purification of two chondroitin lyases fromB stercoris HJ-15

B stercoris HJ-15, which degrades a variety of GAGs including chondroitin sulfates, heparin and heparan sulfate [16], constitutively produced chondroitin lyase activity However, when induced with chondroitin sulfate A, total chondroitin lyase activity increased  fivefold (data not shown) Following ultrasonic disruption of B stercoris HJ-15, the crude extract was subjected to a combination

of QAE-cellulose and DEAE-cellulose column chromatog-raphy to remove interacting proteins Chondroitin ABC lyase activity passed through these columns without binding

to the matrices The effluent was further purified to homogeneity with yield of 2.37% by a series of CM-Sepha-dex C-50 column chromatography (Fig 1), hydroxyapatite column and Sephacryl S-300 gel filtration chromatography, and its final specific activity was 45.7 lmolÆmL)1Æmg)1 (Table 1) Chondroitin AC lyase, which passed through CM-Sephadex C-50 resin without binding, was purified to single band on SDS/PAGE with a yield of 6.28% by a combination of hydroxyapatite column and phosphocellu-lose column chromatography The specific activity of purified chondroitin AC lyase was 57.03 lmolÆmL)1Æmg)1 (Table 1) Discontinuous SDS/PAGE illustrated that chon-droitin ABC lyase and chonchon-droitin AC lyase were appar-ently homogeneous and their molecular mass values were estimated to be 116 and 84 kDa, respectively (Fig 2)

Table 1 Purification summary of chondroitin ABC and AC lyases from B sterocoris HJ-15 One unit (U) is the activity forming 1 lmol disac-charides per min The activity was assayed in 50 m M sodium phosphate buffer, pH 7.0.

Stage Total activity (U) Total protein (mg) Specific activity (UÆmg)1) Chondroitin ABC lyase

QAE-cellulose column chromatography 193.86 243.5 0.8

CM Sephadex C-50 column chromatography 218.03 14.94 14.59

Hydroxyapatite column chromatography 88.34 2.15 41.09

Sephacryl S-300 column chromatography 9.94 0.22 45.7

Chondroitin AC lyase

QAE-cellulose column chromatography 193.86 243.5 0.8

CM-Sephadex C-50 column chromatography 137.14 265.9 0.52

Hydroxyapatite column chromatography 115.74 23 5.03

Phosphocellulose column chromatography 26.3 0.461 57.03

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Characterization of two chondroitin lyases

When the molecular masses of chondroitin ABC and AC

lyases under nondenaturing conditions were determined by

gel filtration, chondroitin ABC and AC lyases were

estimated to be 116 and 170 kDa, respectively It suggests

that chondroitin ABC lyase is composed of one subunit and

chondroitin AC lyase is composed of two identical subunits

The optimal pH values of chondroitin ABC and AC

lyases were determined to be 7.0 and 5.7–6.0 for chondroitin

sulfate A, respectively, and the optimum temperatures for

the maximal activity were 40C and 45–50 C, respectively

(data not shown)

The activity of chondroitin ABC lyase was inhibited by

addition of Ni2+, Mg2+, Zn2+, Cu2+and Co2+

Partic-ularly, Cu2+and Zn2+potently inhibited chondroitin ABC

lyase and chondroitin AC lyase

Heparin competitively inhibited only chondroitin AC

lyase, not chondroitin ABC lyase Its inhibition was

reversible (IC50 was 18 lM) (Fig 3) The addition of

50 mM KCl in 50 mM sodium phosphate buffer slightly

increased the activity of both chondroitin ABC and AC

lyases However, the addition of more than 50 mM salt

inhibited the activity of chondroitin lyases

Both enzymes were inhibited by p-chloromercuriphenyl

sulfonic acid; chondroitin AC lyase was inhibited by

iodoacetic acid as well as p-chloromercuriphenyl sulfonic

acid However, both enzymes were little inhibited by the

other chemical modifying agents (data not shown)

Amino-acid composition analysis revealed that the both

chondroitin lyases contain a large proportion of lysine (data

not shown), consistent with their pI values of 7.9–8.3 The

amino-acid compositions of the chondroitin lyases were

similar, but not identical The pI values of the purified

chondroitin ABC and AC lyases were 7.9 and 8.3,

respectively, slightly higher than those of the previously purified chondroitin ABC lyase of B thetaiotaomicron (pI values 7.9 to 8.0) We analyzed the internal sequences of a peptide obtained by digestion of each enzyme with trypsin (Table 3) The internal sequences of chondroitin ABC and

AC lyase show significantly greater homology of 59 and 80% to Flavobacterial chondroitin AC lyase, and 57 and 33% to B thetaiotaomicron chondroitin ABC lyase previously reported [22–24], respectively However, internal sequences of the present chondroitin lyases did not signi-ficantly greater homology to P vulgaris chondroitin ABC lyase

Substrate specificity of two purified chondroitin lyases Chondroitin ABC lyase depolymerized chondroitin sul-fate A, C and dermatan sulsul-fate (Table 4) When chondro-itin sulfate ABC lyase for chondrochondro-itin sulfate A was taken

as 100%, this enzymes activity for chondroitin sulfate C and dermatan sulfate was 40 and 32%, respectively Chondroitin lyase ABC did not act on hyaluronic acid, heparin and heparan sulfate

Chondroitin AC lyase depolymerized chondroitin sul-fate A and C (Table 4) When chondroitin AC lyase for chondritin sulfate A was taken as 100%, this enzymes activity for chondroitin sulfate C and hyaluronic acid was

Fig 2 SDS/PAGE of the purified chondroitin ABC (A) and AC (B)

lyases at various steps of purification (A) Lane 1, preparation after

crude extract; lane 2, preparation after QAE-cellulose column

chro-matography; lane 3, preparation after CM-Sephadex C-25 column

chromatography; lane 4, preparation after hydroxyapatite ultragel

column chromatography; lane 5, Sephacryl S-300 column

chroma-tography; lane M, marker (B) Lane 1, preparation after CM-Sephadex

C-25 column chromatography; lane 2, preparation after

hydroxyapa-tite ultragel column chromatography; lane 3, preparation after

phos-phocellulose column chromatography; lane M, markers.

Table 2 Effect of divalent metal ions on the activity of chondroitin lyases Final concentration of divalent ion, 1 m M 0.03 U of the homogenously purified enzyme activity was taken as 100%.

Metal ion

Relative activity (%) Chondroitin ABC lyase Chondroitin AC lyase

Fig 3 Inhibitory effect of heparin on chondroitin ABC and AC lyases Solid circle, chondroitin sulfate ABC; solid square, chondroitin AC.

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46 and 67%, respectively However, dermatan sulfate,

heparin, heparan sulfate and acharan sulfate were not

substrates for this enzyme

Kinetic constants of two purified chondroitin lyases

Michaelis–Menten constants were determined using the

optimal reaction conditions in experiments designed to

calculate reaction velocities at each substrate concentration

The Km and Vmax of chondroitin ABC and AC lyases

towards chondroitin sulfate A, dermatan sulfate

(chondro-itin sulfate B), and chondro(chondro-itin sulfate C were determined

(Table 5)

D I S C U S S I O N

B stercorisHJ-15 isolated from human intestine is capable

of producing the GAG degrading enzymes In the present

report, we have purified two chondroitin lyases

CM-Sephadex C-50 chromatography efficiently resolved

chon-droitin sulfate degrading lyases of B stercoris HJ-15 As

Fr-a showed a higher specificity to chondroitin sulfates A

and C, and Fr-b fractions showed a higher specificity to chondroitin sulfates A, B and C, they were considered to be chondroitin AC and ABC lyases, respectively (Fig 1) Chondroitin ABC lyases have been purified previously from three other Gram-negative species, P vulgaris [25],

F heparinum[10–13] and B thetaiotaomicron [14,15] These chondroitin ABC lyases were equally active against chon-droitin sulfates A and C The activity against chonchon-droitin sulfate B was 13–40% of the activity against chondroitin sulfate A However, the purified chondroitin ABC lyase activity for chondroitin sulfate B and C was 32 and 40% against chondroitin sulfate A, respectively Hyaluronic acid was not a substrate for this enzyme The present chondroitin ABC lyase substrate specificity was different to the enzymes previously purified from B thetaiotaomicron, Bacillus sp [6], F heparinum and P vulgaris

Chondroitin AC lyases have also been purified previously from some bacterial species, Arthrobacter aurescens [26],

F heparinum and Aeromonas quefaciens[27] These chon-droitin AC lyases were equally active against chonchon-droitin sulfate A and C The activity against chondroitin sulfate B was not However, the purified chondroitin AC lyase

Table 3 Internal amino-acid sequences of chondroitin lyases from Bacteroides stercoris HJ-15.

B stercoris chondroitin ABC lyase YEYAVLPR

B thetaiotaomicron chondroitin ABC lyase 521YEYMVLIQ 57

B stercoris chondroitin AC lyase PGINHPEQ

B thetaiotaomicron chondroitin ABC lyase 509PGLNMATP 33

Table 4 Substrate specificity of chondroitin lyases Activity on chondroitinase A as the substrate was set at 100%.

Relative activity (%)

B stercoris F heparinuma B thetaiotaomicrona P vulgarisa

a Data from [6,9–14].

Table 5 K m and V max values of chondroitin lyases.

Chondrotin ABC lyase Chondroitin AC lyase Substrate K m (lgÆmL)1) V max (UÆmg)1) K m (lgÆmL)1) V max (UÆmg)1)

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activity for chondroitin sulfate C and hyaluronic acid was

46% and 67% against chondroitin sulfate A, respectively

The present substrate specificity of chondroitin AC lyase

was also different to the previously purified enzymes

Particularly, B thetaiotaomicron belonging to the same

species with B stercoris HJ-15 also produces two

chondro-itin ABC lyases, but did not show the chondrochondro-itin AC lyase

activity The chondroitin lyases from B stercoris HJ-15

were different to the previous purified enzymes from

B thetaiotaomicron

When these chondroitin sulfate ABC and AC lyases were

incubated with chondroitin sulfate A, these enzymes mainly

produced disaccharide and tetrasaccharide/hexasaccharide,

respectively (data not shown) These results suggest that

chondroitin ABC and AC lyases have exolytic and endolytic

action patterns

These chondroitin ABC and AC lyases showed optimal

activity at pH 7.0 and 5.7–6.0 respectively, like most of

previously reported chondroitin lyases which have optimal

pH values in the range 6.0 to 8.0 Most reported

chondroitin lyases had molecular masses between 53 and

118 kDa The molecular masses of chondroitin ABC and

AC lyases were calculated at 83 and 170 kDa by gel

filtration and by SDS/PAGE, respectively These results

suggest that chondroitin ABC lyase is composed of a single

subunit and chondroitin AC lyase is composed of two

identical subunits Amino-acid composition analysis

revealed that the chondroitin ABC and AC lyases contain

a large proportion of lysine, consistent with their pI values

of 7.9–8.3 The pI values of the purified chondroitin lyases

were slightly higher than the previously purified

chondroitin lyases from P vulgaris and B

thetaiotaomi-cron Several attempts at N-terminal analysis failed to

yield sequence information suggesting that the

N-terminus is blocked Therefore, we analyzed the internal

sequences of a peptide obtained by a tryptic digestion The

internal sequences of the chondroitin AC lyase reported

here show significantly greater homology to Flavobacterial

chondroitin AC lyase than to B thetaiotaomicron

chon-droitin ABC lyase Those of the chonchon-droitin ABC lyase

reported here do not show significantly greater homology

to the previously purified chondroitin ABC lyases from

F heparinum, B thetaiotaomicron and P vulgaris than

those of chondroitin AC lyase These results suggest that

the chondroitin AC lyase reported here belongs to the

family of previously purified chondroitin AC lyases, but

the present chondroitin ABC lyase is slightly different from

previously identified chondroitin ABC lyases Molecular

masses, acid composition data and internal

amino-acid sequence homologies of the present chondroitin ABC

lyases were different to the previously reported chondroitin

ABC lyase There were not any divalent metal ions that

activated the enzymes significantly Instead, most of

divalent metal ions except for Mn2+and Ca2+inhibited

the activity of chondroitin lyases Both chondroitin lyases

were potently inhibited by Cu2+and Zn2+ Both enzymes

were potently inhibited by p-chloromercuriphenyl sulfonic

acid This suggests that the active site of these enzymes

may contain a cysteine residue The chondroitin ABC and

AC lyases reported here showed optimal activity at 40C

and 45–50C, respectively The F heparinum chondroitin

ABC and AC lyases had the lowest optimal temperatures,

30C and 40 C, respectively, and the chondroitin ABC

lyases from P vulgaris and B thetaiotaomicron showed optimal activity at 37C The chondroitin lyases reported here were completely inactivated above 60C; i.e they seem to be more stable than the previously purified chondroitin lyases

In conclusion, this is the first report on the purification and characterization of chondroitin ABC and AC lyases, particulary chondroitin AC lyase, from an anaerobic bacterium (B stercoris) in human intestine The substrate specificity and other characteristics of the two chondroitin lyases reported here are different from the previous reported chondroitin lyases

A C K N O W L E D G E M E N T This work was supported by KOSEF grant 1999-2-209-010-5 (D H K and Y S K.) and the BK 21 grant from the Ministry of Education (D H K and Y S K.).

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