Developmental pattern in the formation of various multienzyme complexes associated with Benson-Calvin cycle in cotton leaves

Abstract

An electrophoretically homogeneous preparation of a multienzyme complex with a mol wt of 520 ± 20 kD was isolated from 15- to 25-day-old cotton (Gossypium hirsutum L.) leaves uniform in their age and position on the shoot (3rd to 4th leaves from the top when the plants possessed 5–6 true leaves). When cotton leaves were sampled at the stage of budding and flowering, two complexes with mol wts of 520 ± 20 kD and 480 ± 15 kD were isolated. Comparative enzymatic studies of these complexes revealed developmental changes in activities of ribose phosphate isomerase, phosphoribulokinase, and ribulose-bisphosphate carboxylase. The multienzyme complexes were almost identical in activity of ribose phosphate isomerase. Activities of phosphoribulokinase and ribulose-bisphosphate carboxylase for various multienzyme complexes showed variations between 14 and 17% in the presence of ribose-5-phospate + ATP as a substrate, but the differences were smaller (6–7%) in the presence of specific substrates of these enzymes. The formation of multienzyme Benson-Calvin cycle complexes, featuring different properties at various stages of plant development, is presumably related to the increased demand in assimilates for epigenetic processes during formation of generative organs.