The Enzymatic Cleavage of the Carbon-Nitrogen Bond in 3α,7α,12α-Trihydroxy-5β-cholan-24-oylglycine

Conjugated Bile Acid Hydrolase Is a Tetrameric N-Terminal Thiol Hydrolase with Specific Recognition of Its Cholyl but Not of Its Tauryl Product,

“…Superposition of apo-and tauroCBAH crystal structures did not reveal any significant conformational differences between monomers, the overall root-mean-square deviations being not more than 0.36 Å between C R atoms of monomers as well as tetramers of both crystal forms. This agrees with kinetic data of BSH enzymes that fit the Michaelis-Menten equation (8,9,35), and suggest that CBAH may be described as an enzyme with four independent catalytic sites showing no cooperativity.…”

“…Conservation of the Active Site. It has long been known that cysteine is involved in the catalytic function of C. perfringens CBAH ( , ), and recently, the homologous BSH from Bifidobacterium longum could be inactivated by a single base substitution Cys1 → Ala (), and the more conservative substitutions Cys1 → Ser and Cys1 → Thr inactivated BSH from Bifidobacterium bifidum (). Further residues of the active site have been identified by sequence alignments of penicillin V acylase (PVA) with BSH (), and active site residues in PVA have been identified by comparison with penicillin G acylase (), of which enzyme−inhibitor complexes have been described ().…”

“…Conjugated bile acid hydrolase (CBAH) from C. perfringens [EC 3.5. 1.24] was first shown in 1967 to have catalytic activity toward glycyl-and taurocholic acids (8). The enzyme was purified (9), and the gene encoding CBAH was cloned, sequenced, and shown to be homologous to penicillin V acylase (PVA) from Bacillus sphaericus (10), of which the three-dimensional structure has been determined (11).…”

Electrostatic Interactions Dictate Bile Salt Hydrolase Substrate Preference

“…Although previous literature suggested C. perfringens CGH hydrolyzes LeuCA more readily than TyrCA, 13 we found TyrCA was hydrolyzed to a greater extent than LeuCA (Figure 1b) because C. perfringens show strain-dependent substrate preferences based on the identity of the amino acid conjugate. 36,37 We also found that TyrCA and PheCA had remarkably different amounts of hydrolysis despite comparable steric hindrance near the amide bond, which was a previously identified factor for substrate preference 13 (Figure 1b). These differences in the overall MCBA hydrolysis between CGH and BSH1 suggested distinct substrate selectivity (Figure 1b).…”

Synthesis and intestinal metabolism of ursodeoxycholic acid conjugate with an antiinflammatory agent, 5-aminosalicylic acid

“…The R f value of the compound on TLC was slightly higher than that of glycoursodeoxycholic acid (0.65 vs. 0.60) and it was eluted later than glycoursodeoxycholic acid on HPLC, (8.3 min vs. 7.6 min), thereby suggesting that this conjugate may be of similar hydrophilicity as glycoursodeoxycholic acid. The amide bond was cleaved with strong alkali and when incubated with cholylglycine hydrolase under conditions known to cleave the glycine and taurine conjugates of bile acids (24), free UDCA was obtained with no detectable amounts of the unreacted compound. Similarly, when a pure strain of C. perfringens was grown in chopped meat broth containing UDCA-5-ASA conjugate, free UDCA was quantitatively recovered.…”