Carinato M E, Collin-Osdoby P, Yang X, Knox T M, Conlin C A, Miller C G
Department of Microbiology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
J Bacteriol. 1998 Jul;180(14):3517-21. doi: 10.1128/JB.180.14.3517-3521.1998.
Salmonella typhimurium apeR mutations lead to overproduction of an outer membrane-associated N-acetyl phenylalanine beta-naphthyl ester-cleaving esterase that is encoded by the apeE gene (P. Collin-Osdoby and C. G. Miller, Mol. Gen. Genet. 243:674-680, 1994). This paper reports the cloning and nucleotide sequencing of the S. typhimurium apeE gene as well as some properties of the esterase that it encodes. The predicted product of apeE is a 69.9-kDa protein which is processed to a 67-kDa species by removal of a signal peptide. The predicted amino acid sequence of ApeE indicates that it is a member of the GDSL family of serine esterases/lipases. It is most similar to a lipase excreted by the entomopathogenic bacterium Photorhabdus luminescens. The Salmonella esterase catalyzes the hydrolysis of a variety of fatty acid naphthyl esters and of C6 to C16 fatty acid p-nitrophenyl esters but will not hydrolyze peptide bonds. A rapid diagnostic test reported to be useful in distinguishing Salmonella spp. from related organisms makes use of the ability of Salmonella to hydrolyze the chromogenic ester substrate methyl umbelliferyl caprylate. We report that the apeE gene product is the enzyme in Salmonella uniquely responsible for the hydrolysis of this substrate. Southern blot analysis indicates that Escherichia coli K-12 does not contain a close analog of apeE, and it appears that the apeE gene is contained in a region of DNA present in Salmonella but not in E. coli.
鼠伤寒沙门氏菌apeR基因突变导致一种与外膜相关的N-乙酰苯丙氨酸β-萘酯裂解酯酶过量产生，该酯酶由apeE基因编码（P. 科林 - 奥斯多比和C. G. 米勒，《分子与普通遗传学》243:674 - 680，1994）。本文报道了鼠伤寒沙门氏菌apeE基因的克隆和核苷酸测序，以及它所编码的酯酶的一些特性。apeE的预测产物是一种69.9 kDa的蛋白质，通过去除信号肽可加工成67 kDa的形式。ApeE的预测氨基酸序列表明它是丝氨酸酯酶/脂肪酶GDSL家族的成员。它与昆虫致病细菌发光杆菌分泌的一种脂肪酶最为相似。沙门氏菌酯酶催化多种脂肪酸萘酯和C6至C16脂肪酸对硝基苯酯的水解，但不会水解肽键。据报道，一种用于区分沙门氏菌属与相关生物体的快速诊断测试利用了沙门氏菌水解显色酯底物辛酸甲基伞形酮的能力。我们报道apeE基因产物是沙门氏菌中唯一负责水解该底物的酶。Southern印迹分析表明大肠杆菌K - 12不含有apeE的紧密类似物，并且apeE基因似乎存在于沙门氏菌而非大肠杆菌的一段DNA区域中。
