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B6db references: 21982920

type Journal Article
authors Karsten WE, Reyes ZL, Bobyk KD, Cook PF, Chooback L.
title Mechanism of the aromatic aminotransferase encoded by the Aro8 gene from Saccharomyces cerevisiae
journal Arch Biochem Biophys
sel selected
ui 21982920
year (2011)
volume 516
number 1
pages 67-74
abstract The amino acid l-lysine is synthesized in Saccharomyces cerevisiae via the α-aminoadipate pathway. An as yet unidentified PLP-containing aminotransferase is thought to catalyze the formation of α-aminoadipate from α-ketoadipate in the l-lysine biosynthetic pathway that could be the yeast Aro8 gene product. A screen of several different amino acids and keto-acids showed that the enzyme uses l-tyrosine, l-phenylalanine, α-ketoadipate, and l-α-aminoadipate as substrates. The UV-visible spectrum of the aminotransferase exhibits maxima at 280 and 343nm at pH 7.5. As the pH is decreased the peak at 343nm (the unprotonated internal aldimine) disappears and two new peaks at 328 and 400nm are observed representing the enolimine and ketoenamine tautomers of the protonated aldimine, respectively. Addition, at pH 7.1, of α-ketoadipate to free enzyme leads to disappearance of the absorbance at 343nm and appearance of peaks at 328 and 424nm. The V/E(t) and V/K(α-ketoadipate)E(t) pH profiles are pH independent from pH 6.5 to 9.6, while the V/K(l)(-tyrosine) pH-rate profile decreases below a single pK(a) of 7.00.1. Data suggest the active enzyme form is with the internal aldimine unprotonated. We conclude the enzyme should be categorized as a α-aminoadipate aminotransferase.
last changed 2017/07/14 13:26

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