Dg. Abraham et al., ISOLATION FROM RAT-KIDNEY OF A CYTOSOLIC HIGH-MOLECULAR-WEIGHT CYSTEINE-S-CONJUGATE BETA-LYASE WITH ACTIVITY TOWARD LEUKOTRIENE E(4), The Journal of biological chemistry, 270(1), 1995, pp. 180-188
A cytosolic high M(r) cysteine-S-conjugate beta-lyase (apparent M(r) o
f similar to 330,000) has been partially purified from rat kidneys. Th
e high M(r) lyase is also present in the mitochondria, The purified en
zyme contains at least two proteins with apparent M(r) values of simil
ar to 50,000 and similar to 70,000. Activity is stimulated by dithioth
reitol, alpha-keto acids, and pyridoxal 5'-phosphate; aminooxyacetate
is an inhibitor. The enzyme catalyzes a competing (half) transaminatio
n reaction between pyridoxal 5'-phosphate cofactor and cysteine-S-conj
ugate substrate; added alpha-keto acids promote conversion of active s
ite pyridoxamine 5'-phosphate to pyridoxal 5'-phosphate. The enzyme al
so catalyzes a full (but weak) transamination between L-phenylalanine
and alpha-keto-gamma-methiolbutyrate. The purified enzyme is not recog
nized by polyclonal rabbit antibodies to cytosolic rat kidney glutamin
e transaminase K (another cysteine-S-conjugate beta-lyase of rat kidne
y) and has no obvious similarities to other pyridoxal 5'-phosphate-con
taining enzymes. In addition to catalyzing elimination reactions with
S-(1,2-dichlorovinyl)-L-cysteine and S-(1,1,2,2-tetrafluoroethyl)-L-cy
steine, the enzyme reacts with leukotriene E(4) and 5'-S-cysteinyldopa
mine. Finally, the cytosolic and mitochondrial enzymes are activated b
y alpha-ketoglutarate. Thus, the possibility must be considered that,
in kidneys of animals exposed to various cysteine conjugates, the high
M(r) lyase contributes to the generation of pyruvate, ammonia, and re
active fragments in vivo. Many cysteine conjugates are nephrotoxic, an
d the high M(r) lyase(s) may be involved.