Yh. Tsai et al., A NOVEL CALCIUM-INDEPENDENT ENZYME CAPABLE OF INCORPORATING PUTRESCINE INTO PROTEINS, Biochemical and biophysical research communications, 244(1), 1998, pp. 161-166
A Ca++-independent enzyme capable of incorporating [H-3]-putrescine in
to proteins was detected in the rat intestine mucosa. The Ca++-indepen
dent incorporation of [H-3]-putrescine into proteins was temperature-,
pH-, time-, and dose-dependent. However, this enzyme was absent in th
e gastric mucosa. Similar to testicular Ca++-dependent transglutaminas
e, the optimal pH of intestinal Ca++-independent enzyme was 9.0. At 10
(-5) M or less putrescine concentrations, the Ca++-independent enzyme
in an intestinal cytosol preparation showed a greater activity than di
d the Ca++-dependent transglutaminase. However, at higher putrescine c
oncentrations, the latter showed a greater activity than did the forme
r. Both the intestinal Ca++-dependent and independent enzymes were inh
ibited by cystamine, thermal labile at 50 degrees C and precipitated b
y 30 to 50% saturation of ammonium sulfate. The fact that these two en
zymes shared many similar characteristics, with the exceptions of Ca+-requirement, suggests that they may have similar active site and intr
insic molecular function(s). (C) 1998 Academic Press.