Dg. Abraham et Ajl. Cooper, CLONING AND EXPRESSION OF A RAT-KIDNEY CYTOSOLIC GLUTAMINE TRANSAMINASE-K THAT HAS STRONG SEQUENCE HOMOLOGY TO KYNURENINE PYRUVATE AMINOTRANSFERASE, Archives of biochemistry and biophysics, 335(2), 1996, pp. 311-320
An alpha-keto acid-dependent cysteine S-conjugate beta-lyase of rat ki
dney was identified as cytosolic glutamine transaminase K by Stevens e
t al. (J. Biol. Chem. 261, 15529-15537, 1986), Subsequently, a rat kid
ney protein with both glutamine transaminase K- and cysteine S-conjuga
te beta-lyase activities was cloned and sequenced by Ferry et al. (Mol
. Pharmacol, 43, 660-665, 1993). This protein was later shown to be id
entical with kynurenine pyruvate aminotransferase (Mosca et al., FEES
Lett, 353, 21-24, 1994), Thus, kynurenine pyruvate aminotransferase po
ssesses both glutamine transaminase K- and cysteine S-conjugate beta-l
yase-type activities, We have also cloned a cytosolic glutamine transa
minase 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. O
ur 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 catal
yze glutamine transaminase K/cysteine S-conjugate beta-lyase/kynurenin
e pyruvate aminotransferase reactions, The present work underscores th
e difficulties associated with characterizing aminotransferases with o
verlapping specificities. (C) 1996 Academic Press, Inc.