Inhibitory effect of zinc and copper on phosphatase activity in the brain cytosol of rats: involvement of SH groups.
The effect of various metal ions on neutral phosphatase activity in the brain cytosol of rats was investigated. p-Nitrophenylphosphate was used as the substrate for the enzyme assay. Brain cytosolic phosphatase activity was significantly decreased by the presence of zinc or copper in the range of 10(-5) to 10(-3) M in the enzyme reaction mixture, while it was significantly increased by manganese, nickel or cobalt (10(-5) to 10(-3) M). Calcium (10(-5) to 10(-3) M) did not have an appreciable effect on brain cytosolic phosphatase activity. The inhibitory effect of zinc (10(-5) M) or copper (10(-5) M) on phosphatase activity was seen in the presence of manganese, nickel or cobalt with 10(-4) M concentration, indicating a potent inhibitory effect of these metals. Zinc or copper-decreased phosphatase activity was clearly prevented by dithiothreitol (5 mM), although the effect of each metal was further enhanced by N-ethylmaleimide (5 mM), suggesting that the metals act on the SH-groups of enzyme. Moreover, the inhibitory effect of zinc (10(-5) M) was significantly enhanced by S-100A (10(-6) M) or calbindin (10(-7) M), although neither protein had any effect in the presence of calcium (10(-5) M) or copper (10(-5) M). These results suggests that zinc has an unique role in the regulation of neutral phosphatase activity in rat brain cytosol.
Hanahisa
Y
Y
Laboratory of Endocrinology and Molecular Metabolism, Graduate School of Nutritional Sciences, University of Shizuoka, Japan.
Yamaguchi
M
M
D000818:Animals; D001921:Brain / Q000201:enzymology* / Q000378:metabolism; D064026:Calbindins; D003300:Copper / Q000494:pharmacology*; D003600:Cytosol / Q000201:enzymology / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005260:Female; D010744:Phosphoric Monoester Hydrolases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D064030:S100 Calcium Binding Protein G / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000378:metabolism; D015032:Zinc / Q000494:pharmacology*
D064026:Calbindins; D004791:Enzyme Inhibitors; D064030:S100 Calcium Binding Protein G; D013438:Sulfhydryl Compounds; D003300:Copper; D010744:Phosphoric Monoester Hydrolases; D015032:Zinc