Đang chuẩn bị nút TẢI XUỐNG, xin hãy chờ
Tải xuống
The Escherichia coli bifunctional T-protein transforms chorismic acid to p-hydroxyphenylpyruvic acid in the L-tyrosine biosynthetic pathway. The 373 amino acid T-protein is a homodimer that exhibits chorismate mutase (CM) and prephenate dehydrogenase (PDH) activities, both of which are feedback-inhibited by tyrosine. Fifteen genes coding for the T-protein and various fragments thereof were constructed and successfully expressed in order to charac-terize theCM, PDHand regulatory domains. | Eur. J. Biochem. 270 757-763 2003 FEBS 2003 doi 10.1046 j.1432-1033.2003.03438.x Mapping of chorismate mutase and prephenate dehydrogenase domains in the Escherichia coli T-protein Shuqing Chen1 I Sarah Vincent2 David B. Wilson1 and Bruce Ganem2 1 Department of Molecular Biology and Genetics and department of Chemistry and Chemical Biology Cornell University NY USA The Escherichia coli bifunctional T-protein transforms chorismic acid to p-hydroxyphenylpyruvic acid in the L-tyrosine biosynthetic pathway. The 373 amino acid T-protein is a homodimer that exhibits chorismate mutase CM and prephenate dehydrogenase PDH activities both of which are feedback-inhibited by tyrosine. Fifteen genes coding for the T-protein and various fragments thereof were constructed and successfully expressed in order to characterize the CM PDH and regulatory domains. Residues 1-88 constituted a functional CMdomain which was also dimeric. Both the PDH and the feedback-inhibition activities were localized in residues 94-373 but could not be separated into discrete domains. The activities of cloned CMand PDH domains were comparatively low suggesting some cooperative interactions in the native state. Activity data further indicate that the PDH domain in which NAD prephenate and tyrosine binding sites were present was more unstable than the CMdomain. Keywords chorismate mutase E. coli T-protein prephenate dehydrogenase. The final step in the biosynthesis of tyrosine in Escherichia coli and other enteric bacteria is the transamination of p-hydroxyphenylpyruvate which is produced in two sequential chemical reactions from chorismic acid in nature s shikimic acid metabolic pathway 1 2 . In the first reaction chorismate undergoes a Claisen rearrangement to form prephenate which is catalyzed by chorismate mutase CM EC 5.4.99.5 . In the second reaction prephenate undergoes NAD -mediated oxidative decarboxylation to p-hydroxyphenylpyruvate which is catalyzed by prephenate dehydrogenase PDH EC 1.3.1.12
