Malate Dehydrogenase and Other Enzymes

Abstract

The activity and some properties of NADH malate dehydrogenase in extracts of marine plants was investigated. Activity was detected in 24 species examined and average rates [in µmol min-1 (mg chlorophyll)-1] in the major groups were: Cyanophyta, 47; Chlorophyta, 74; Phaeophyta, 35; Rhodophyta, 69; and Anthophyta, 150. The zooxanthellae of clams and coral also showed substantial NADH malate dehydrogenase activity [4-63 µmol min-1 (mg chlorophyll)-1]. Some kinetic properties of the enzyme from Halimeda cylindracea were studied and the inhibition of enzyme activity by NaCl and sea water was examined. The activity of NADP malate dehydrogenase (decarboxylating) was measured in several organisms [0.15 - 5.0 µmol min-1 (mg chlorophyll)-1] and the presence of low activity phosphoenolpyruvate carboxylase was qualitatively established. These observations are discussed in relation to pathways of CO*2 metabolism in marine plants.