Roles of Calmodulin Dependent and Independent NAD Kinases in Regulation of Nicotinamide Coenzyme Levels of Green Plant Cells

Abstract

Light-induced conversion of NAD to NADP occurs in algal cells (Oh-hama and Miyachi, 1959) and higher plant leaves (Ogren and Krogman, 1965). The conversion was highly associated with photosynthetic electron transport and photophosphorylation (Matsumura-Kadota et al., 1982). Studies with protoplasts and intact chloroplasts isolated from higher plant leaves showed that the conversion reaction occurred in the chloroplasts and that NAD kinase by which this reaction was catalyzed, was mostly localized in the chloroplasts (Muto et al., 1981). During purification from pea seedlings, NAD kinase was totally inactivated because of the removal of a protein activator (Muto and Miyachi, 1977), which was subsequently identified as calmodulin (CaM) (Anderson and Cormier, 1978; Anderson et al., 1980). Recently, we found that CaM concentration in the chloroplast was sufficent to saturate NAD kinase located therein (Muto, 1982), and tha the intact chloroplasts from wheat and spinach leaves actively took up Ca²⁺ when illuminated (Muto et al., 1982).