Chloroplast class I and class II aldolases are bifunctional for fructose-1,6-biphosphate and sedoheptulose-1,7-biphosphate cleavage in the Calvin cycle

Abstract

Class I and class II aldolases are products of two evolutionary non-related gene families. The cytosol and chloroplast enzymes of higher plants are of the class I type, the latter being bifunctional for fructose-1,6- and sedoheptulose-1,7-P2 in the Calvin cycle. Recently, class II aldolases were detected for the cytosol and chloroplasts of the lower alga Cyanophora paradoxa. The respective chloroplast enzyme has been shown here to be also bifunctional for fructose-1,6- and sedoheptulose-1,7-P2. Kinetics, also including fructose-1-P, were determined for all these enzymes. Apparently, aldolases are multifunctional enzymes, irrespective of their class I or class II type.