Effects of Calcium on NAD(H)-Glutamate Dehydrogenase from Turnip (Brassica rapa L.) Mitochondria |
| |
Authors: | Itagaki Tadashi; Dry Ian B; Wiskich Joseph T |
| |
Institution: | 1Botany Department, The University of Adelaide Adelaide, S.A. 5001, Australia |
| |
Abstract: | The effect of Ca2+ and ammonia on mitochondrial NADH-glutamatedehydrogenase (GDH: EC 1.4.1.2
EC]
) isolated from turnip root (Brassicarapa L.) activity was examined. Increasing the ammonia (NH4)2SO4]concentration led to significant substrate inhibition whichcould be reversed by micromolar levels of Ca2+. The sensitivityof the enzyme to ammonia inhibition and its reversal by Ca2+was affected by proteolysis. After treatment with various proteases,lower concentrations of Ca2+ were capable of fully activatingthe enzyme or overcoming the inhibitory effects of high ammonium,compared to non-treated enzyme. However, the protease-treatedenzyme was still sensitive to ethylene glycol-bis(ß-aminoethylether) N,N,N',N'-tetraacetate (EGTA). In contrast, NADH-GDHactivity was inhibited approx. 30% by organic mercurials (200µm), but the residual activity was not affected by thesubsequent additions of EGTA. NADH-GDH activity could also bestimulated by additions of high concentrations of NaCl (300mM) in the absence of added Ca2+. These results suggest thathydrophobic and -SH groups may be involved in the regulationof mitochondrial NADH-GDH activity by Ca2+.
2 Present address: CSIRO Division of Horticulture, Urrbrae,S.A. 5064, Australia (Received April 18, 1990; Accepted July 23, 1990) |
| |
Keywords: | |
本文献已被 Oxford 等数据库收录! |
|