Bora P S, Miller D D, Chaitman B R
Department of Internal Medicine, St. Louis University Health Sciences Center, John Cochran VA Medical Center, Missouri 63110, USA.
Mol Cell Biochem. 1998 Mar;180(1-2):111-5.
Fatty acid ethyl ester synthase-III metabolizes both ethanol and carcinogens. Structure-function studies of the enzyme have not been performed in relation to site specific mutagenesis. In this study, three residues (Gly 32, Cys 39 and His 72) have been mutated to observe their role in enzyme activity. Gly to Gln, Cys to Trp and His to Ser mutations did not affect fatty acid ethyl ester synthase activity, but His to Ser mutant had less than 9% of control glutathione S-transferase activity. The apparent loss of transferase activity reflected a 28 fold weaker binding constant for glutathione. Thus, this study indicates that Gly and Cys may not be important for synthase or transferase activities however, histidine may play a role in glutathione binding, but it is not an essential catalytic residue of glutathione S-transferase or for fatty acid ethyl ester synthase activity.
脂肪酸乙酯合酶III既能代谢乙醇又能代谢致癌物。尚未针对位点特异性诱变对该酶进行结构-功能研究。在本研究中，三个残基（甘氨酸32、半胱氨酸39和组氨酸72）发生了突变，以观察它们在酶活性中的作用。甘氨酸突变为谷氨酰胺、半胱氨酸突变为色氨酸以及组氨酸突变为丝氨酸的突变均未影响脂肪酸乙酯合酶活性，但组氨酸突变为丝氨酸的突变体的谷胱甘肽S-转移酶活性不到对照的9%。转移酶活性的明显丧失反映出谷胱甘肽的结合常数减弱了28倍。因此，本研究表明，甘氨酸和半胱氨酸可能对合酶或转移酶活性并不重要，然而，组氨酸可能在谷胱甘肽结合中发挥作用，但它不是谷胱甘肽S-转移酶的必需催化残基，也不是脂肪酸乙酯合酶活性所必需的。
