Li Y, Chen J, Jiang W, Mao X, Zhao G, Wang E
State Key Laboratory of Molecular Biology, Shanghai Institute of Biochemistry, Academia Sinica, China.
Eur J Biochem. 1999 Jun;262(3):713-9. doi: 10.1046/j.1432-1327.1999.00417.x.
Cephalosporin acylases are a group of enzymes that hydrolyze cephalosporin C (CPC) and/or glutaryl 7-amino cephalosporanic acid (GL-7ACA) to produce 7-amino cephalosporanic acid (7-ACA). The acylase from Pseudomonas sp. 130 (CA-130) is highly active on GL-7ACA and glutaryl 7-aminodesacetoxycephalosporanic acid (GL-7ADCA), but much less active on CPC and penicillin G. The gene encoding the enzyme is expressed as a precursor polypeptide consisting of a signal peptide followed by alpha- and beta-subunits, which are separated by a spacer peptide. Removing the signal peptide has little effect on precursor processing or enzyme activity. Substitution of the first residue of the beta-subunit, Ser, results in a complete loss of enzyme activity, and substitution of the last residue of the spacer, Gly, leads to an inactive and unprocessed precursor. The precursor is supposed to be processed autocatalytically, probably intramolecularly. The two subunits of the acylase, which separately are inactive, can generate enzyme activity when coexpressed in Escherichia coli. Data on this and other related acylases indicate that the cephalosporin acylases may belong to a novel class of enzymes (N-terminal nucleophile hydrolases) described recently.
头孢菌素酰化酶是一类能够水解头孢菌素C（CPC）和/或戊二酰7-氨基头孢烷酸（GL-7ACA）以产生7-氨基头孢烷酸（7-ACA）的酶。来自假单胞菌属130（CA-130）的酰化酶对GL-7ACA和戊二酰7-氨基去乙酰氧基头孢烷酸（GL-7ADCA）具有高活性，但对CPC和青霉素G的活性则低得多。编码该酶的基因表达为一种前体多肽，其由信号肽、随后是α亚基和β亚基组成，α亚基和β亚基由间隔肽分隔。去除信号肽对前体加工或酶活性几乎没有影响。β亚基的第一个残基丝氨酸被取代会导致酶活性完全丧失，间隔肽的最后一个残基甘氨酸被取代会导致前体无活性且未加工。前体应该是通过自身催化进行加工的，可能是分子内加工。酰化酶的两个亚基单独时无活性，但在大肠杆菌中共表达时可以产生酶活性。关于这种及其他相关酰化酶的数据表明，头孢菌素酰化酶可能属于最近描述的一类新型酶（N-末端亲核水解酶）。
