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B6db references: 97072095

type Journal Article
authors Abraham, D. G.; Cooper, A. J.
title Cloning and expression of a rat kidney cytosolic glutamine transaminase K that has strong sequence homology to kynurenine pyruvate aminotransferase
journal Arch Biochem Biophys
ui 97072095
year (1996)
volume 335
number 2
pages 311-20.
keywords Amino Acid Sequence
abstract An alpha-keto acid-dependent cysteine S-conjugate beta-lyase of rat kidney was identified as cytosolic glutamine transaminase K by Stevens et al. (J. Biol. Chem. 261, 15529-15537, 1986). Subsequently, a rat kidney protein with both glutamine transaminase K- and cysteine S- conjugate beta-lyase activities was cloned and sequenced by Perry et al. (Mol. Pharmacol. 43, 660-665, 1993). This protein was later shown to be identical with kynurenine pyruvate aminotransferase (Mosca et al., FEBS Lett. 353, 21-24, 1994). Thus, kynurenine pyruvate aminotransferase possesses both glutamine transaminase K- and cysteine S-conjugate beta-lyase-type activities. We have also cloned a cytosolic glutamine transaminase K from a rat kidney cDNA library and expressed the full-length clone in COS1 cells. The transfected cells exhibit marked increases in activities of both glutamine transaminase K and cysteine S-conjugate beta-lyase. The enzyme cloned in the present work is a homodimer. Each subunit has a molecular mass of 45.8 kDa and contains 426 amino acid residues. The sequence of cytosolic glutamine transaminase K obtained in the present work has strong similarities to other aminotransferases, including >90% identity with kynurenine pyruvate aminotransferase. Our preparation of purified rat kidney cytosolic glutamine transaminase K possesses some kynurenine pyruvate aminotransferase activity. Thus, rat kidney cytosol possesses at least two distinct enzymes that catalyze glutamine transaminase K/cysteine S- conjugate beta-lyase/kynurenine pyruvate aminotransferase reactions. The present work underscores the difficulties associated with characterizing aminotransferases with overlapping specificities.
last changed 2002/11/12 16:17

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