Sawai T, Yamaguchi A, Tsukamoto K
Division of Microbial Chemistry, Faculty of Pharmaceutical Sciences, Chiba University, Japan.
Rev Infect Dis. 1988 Jul-Aug;10(4):721-5. doi: 10.1093/clinids/10.4.721.
The structural gene for a cephalosporinase of Citrobacter freundii GN346 was sequenced. From the nucleotide sequence, the entire amino acid sequence of the mature enzyme with 361 amino acids and a molecular weight of 39,867 was determined. The active-site serine was directly confirmed to be serine 64 by studies in which the enzyme was labeled with dansylpenicillin. In investigations comparing the inhibitory effect of sulbactam (penicillanic acid sulfone) and cloxacillin sulfone on the cephalosporinase and on TEM-2-type penicillinase, sulbactam was found to be an effective progressive inhibitor but a poor competitive inhibitor for the cephalosporinase. The cephalosporinase and the inhibitor formed a long-lived complex with a half-life of 550 minutes. Cloxacillin sulfone could not inactivate the cephalosporinase progressively but irreversibly inactivated the penicillinase.
对弗氏柠檬酸杆菌GN346的一种头孢菌素酶的结构基因进行了测序。根据核苷酸序列，确定了成熟酶的完整氨基酸序列，该酶含361个氨基酸，分子量为39,867。通过用丹磺酰青霉素标记该酶的研究，直接证实活性位点丝氨酸为第64位丝氨酸。在比较舒巴坦（青霉烷酸砜）和氯唑西林砜对头孢菌素酶和TEM-2型青霉素酶抑制作用的研究中，发现舒巴坦是头孢菌素酶的一种有效的渐进性抑制剂，但竞争性较差。头孢菌素酶与抑制剂形成了一种半衰期为550分钟的长寿命复合物。氯唑西林砜不能使头孢菌素酶逐渐失活，但能不可逆地使青霉素酶失活。
