Duez C, Frère J M, Klein D, Noël M, Ghuysen J M, Delcambe L, Dierickx L
Biochem J. 1981 Jan 1;193(1):75-82. doi: 10.1042/bj1930075.
The exocellular beta-lactamase of Streptomyces albus G has been purified to near protein homogeneity. It consists of one single polypeptide chain of mol.wt. 30 000-31 000, has a rather low isoelectric point (at pH 6.0) and contains less lysine (2.1%) and more half-cystine residues than most beta-lactamases from other Gram-positive bacteria. Penicillins are much better substrates than delta 3-cephalosporins; the catalytic-centre activity of good penicillin substrates is 333-500 s-1. The exocellular, mol.wt. 17 000 DD-carboxypeptidase of S. albus G [previously purified to protein homogeneity; Duez, Frère, Geurts, Ghuysen, Dierickx & Delcambe (1978) Biochem. J. 175, 793-800] behaves as an exceedingly poor beta-lactamase, hydrolysing benzylpenicillin into benzylpenicilloate 5 x 10(-6)-fold less rapidly than does the exocellular beta-lactamase. To all appearances, the beta-lactamase has no bivalent cation requirement whereas, as shown elsewhere [Dideberg, Charlier, Dupont, Vermeire, Frère & Ghuysen (1980) FEBS Lett. 117, 212-214, and Dideberg, Joris, Frère, Ghuysen, Weber, Robaye, Delbrouck & Roelands (1980) FEBS Lett. 117, 215-218], the DD-carboxypeptidase possesses one essential Zn2+ ion per molecule. Peptide 'mapping' and immunological studies suggest that the two Streptomyces enzymes probably have very different structural and mechanistic properties.
白色链霉菌G的胞外β-内酰胺酶已被纯化至接近蛋白质均一性。它由一条分子量为30000 - 31000的单一多肽链组成，等电点相当低（pH 6.0），与大多数其他革兰氏阳性菌的β-内酰胺酶相比，赖氨酸含量较少（2.1%），半胱氨酸残基较多。青霉素是比δ3-头孢菌素更好的底物；良好青霉素底物的催化中心活性为333 - 500 s-1。白色链霉菌G的胞外分子量为17000的DD-羧肽酶[先前已纯化至蛋白质均一性；Duez、Frère、Geurts、Ghuysen、Dierickx和Delcambe（1978年）《生物化学杂志》175卷，793 - 800页]作为一种极其低效的β-内酰胺酶，水解苄青霉素生成苄青霉素酸的速度比胞外β-内酰胺酶慢5×10-6倍。从表面上看，β-内酰胺酶不需要二价阳离子，而正如在其他地方所表明的[Dideberg、Charlier、Dupont、Vermeire、Frère和Ghuysen（1980年）《欧洲生物化学学会联合会快报》117卷，212 - 214页，以及Dideberg、Joris、Frère、Ghuysen、Weber、Robaye、Delbrouck和Roelands（1980年）《欧洲生物化学学会联合会快报》117卷，215 - 218页]，DD-羧肽酶每个分子含有一个必需的Zn2+离子。肽“图谱”和免疫学研究表明，这两种链霉菌酶可能具有非常不同的结构和作用机制特性。
