Non-Enzymatic Glycosylation (or Glycation) and Inhibition of the Pig Heart Cytosolic Aspartate Aminotransferase by Glyceraldehyde 3-Phosphate.
Glyceraldehyde 3-phosphate (Glyc3P), a glycolytic intermediate, non-enzymatically glycosylated (or glycated) and inhibited the pig heart cytoplasmic aspartate aminotransferase (cAAT). Glyc3P (5.0 mM) decreased cAAT activity by 47% after 1 min at 23 degrees C. cAAT activity remained unchanged after a 24 h incubation with either glucose 6-phosphate (5.0 mM) or ribose 5-phosphate (5.0 mM). Increasing the incubation pH from 6.4 to 7.8 or the incubation temperature from 23 degrees C to 50 degrees C enhanced Glyc3P's inhibitory effect on cAAT activity. Glyc3P (250-500 µM) decreased the thermal stability of cAAT as evidenced by lowering the T(m) or temperature that caused a 50% irreversible loss of cAAT activity (69 degrees C, control; 58.5 degrees C, 500 µM Glyc3P). Glyc3P decreased cAAT amino group content and increased glycation products, which were measured by adduct formation, fluorescence and protein crosslinking.
Department of Biochemistry, University of Health Sciences, 1750 Independence Boulevard, Kansas City, MO 64106-1453, USA.
C
Fitzgerald
TA
Swearengin
G
Yeargans
D
McWhorter
B
Cucchetti
NW
Seidler