Abstract
Biochemical properties of thylakoid membrane inorganic pyrophosphatase (PPase) from spinach were investigated in this study. Mg2+ (5 mM) markedly stimulated the PPase activity under alkaline pH values. The native substrate for the hydrolytic reaction of PPase appeared to be magnesium-pyrophosphate. Among anions investigated, only F- caused severe inhibition. Illumination had no effect on PPase activity, indicating its independence of photosynthetic electron transport and associated energization reactions. Radiation inactivation analysis showed that the functional size of PPase was 86.9±4.3 kDa. Group specific modification of the enzyme demonstrated the presence of essential -SH group at the active site which was embedded in the membrane of thylakold.