Open AccessThe Reversible Depolymerization of Spinach Chloroplast Glyceraldehyde‐Phosphate Dehydrogenase
Author(s) -
PUPILLO Paolo,
PICCARI Giovanna GIULIANI
Publication year - 1975
Publication title -
european journal of biochemistry
Language(s) - English
Resource type - Journals
eISSN - 1432-1033
pISSN - 0014-2956
DOI - 10.1111/j.1432-1033.1975.tb03947.x
Subject(s) - dithiothreitol , dehydrogenase , gtp' , nad+ kinase , depolymerization , nucleotide , cooperativity , biochemistry , chemistry , spinach , cooperative binding , glyceraldehyde , stereochemistry , glyceraldehyde 3 phosphate dehydrogenase , chloroplast , allosteric regulation , enzyme , organic chemistry , gene
1 The ligand‐dependent dissociation of spinach chloroplast glyceraldehyde‐phosphate dehydrogenase ( M r 6) to protomers of M r , about 145000, previously shown by us in 1973, has been further characterized by the technique of velocity sedimentation in sucrose gradients. The process exhibits cooperativity and is accompanied by an increase of the apparent NADP + ‐dependent activity (reactivation) from a ratio of 0.1–0.2 to a ratio of 1 to 2 with respect to the NAD + ‐dependent activity. In addition to NADP + and NADPH, most nucleotide triphosphates and, to some extent, P i , act as dissociating agents. The enzyme is depolymerized and progressively inactivated in the presence of 2′‐AMP. 2 Incubation with 20 mM dithiothreitol or 8–10 mM GTP increases the apparent NADP(H)‐dependent activity, although addition of a small amount of a dissociating compound, such as 0.06 mM NADP + , is required for depolymerization. 3 NAD + , NADH and, to a lesser extent, glyceraldehyde 3‐phosphate, NMN and cyclic AMP act as inhibitors of the dissociation and reactivation, however induced. They also favour the re‐association of protomers to tetramers. 4 The NADP(H)‐linked activity is probably a property of the protomers only. The system described here resembles in many respects the light‐dependent regulation of the NADP(H)‐linked activity in vivo.