Politino M, Tonzi S M, Burnett W V, Romancik G, Usher J J
Department of Enzyme Development, Bristol-Myers Squibb Company, Syracuse, New York 13221-4755, USA.
Appl Environ Microbiol. 1997 Dec;63(12):4807-11. doi: 10.1128/aem.63.12.4807-4811.1997.
A novel cephalosporin esterase (EC 3.1.1.41) from Rhodosporidium toruloides was purified to gel electrophoretic homogeneity. The enzyme is a glycoprotein with a molecular mass of 80 kDa. Upon deglycosylation, several forms of the enzyme were observed with a molecular mass range between 60 and 66 kDa. The isoelectric point of the enzyme is approximately 5.6, with the pH optimum for activity occurring at 6.0. The optimal activity of the enzyme occurred at 25 degrees C, with the enzyme rapidly losing activity at temperatures above 25 degrees C. The enzyme deacetylated a variety of cephalosporin derivatives, including cephalosporin C; the Km for this substrate is 51.8 mM, and the Vmax is 7.9 mumol/min/mg. In addition to cephalosporins, the enzyme hydrolyzed short-chain p-nitrophenyl esters, with the activity decreasing with increasing ester chain length. The enzyme also has the ability to acetylate desacetyl cephalosporins in high yields under mild conditions in the presence of various acetyl donors. A comparison of the physical properties of the esterase with those of other well-characterized cephalosporin esterases indicates that the enzyme is unique in this class.
从球拟酵母中纯化出一种新型头孢菌素酯酶（EC 3.1.1.41），达到凝胶电泳均一性。该酶是一种糖蛋白，分子量为80 kDa。去糖基化后，观察到几种分子量在60至66 kDa之间的酶形式。该酶的等电点约为5.6，最适pH值为6.0。酶的最佳活性出现在25℃，在高于25℃的温度下酶活性迅速丧失。该酶可使多种头孢菌素衍生物脱乙酰化，包括头孢菌素C；该底物的Km为51.8 mM，Vmax为7.9 μmol/min/mg。除了头孢菌素外，该酶还能水解短链对硝基苯酯，且活性随酯链长度增加而降低。在各种乙酰供体存在的温和条件下，该酶还具有高产率乙酰化去乙酰头孢菌素的能力。将该酯酶的物理性质与其他已充分表征的头孢菌素酯酶进行比较表明，该酶在这一类中是独特的。
