Transient inhibition by ribose 5-phosphate of photosynthetic O2 evolution in a reconstituted chloroplast system.
Biochim Biophys Acta
; 430(1): 154-64, 1976 Apr 09.
Article
em En
| MEDLINE
| ID: mdl-1260044
ABSTRACT
Photosynthetic oxygen evolution by a reconstituted chloroplast system utilising sn-phospho-3-glycerol (3-phosphoglycerate) ceases upon the addition of ribose 5-phosphate even though the presence of this metabolite permits a rapid and immediate CO2 fixation. The period of cessation is appreciable at 0.1 mM ribose 5-phosphate. It is lengthened as the amount of added ribose 5-phosphate is increased and by the addition of dithiothreitol, a known activator of ribulose-5-phosphate kinase. Ribulose 1,5-bisphosphate is without effect. A similar interruption of O2 evolution may also be brought about by the addition of ADP or by ADP-generating systems such as glucose plus hexokinase. Spectrophotometric experiments indicate that the reoxidation of NADPH in the presence of sn-phospho-3-glycerol is similarly affected. The transient inhibition by ribose 5-phosphate is not observed in the presence of an active ATP-generating system or in the presence of sufficient DL-glyceraldehyde to inhibit ribulose-5-phosphate kinase activity. It is concluded that ribose 5-phosphate inhibits photosynthetic O2 evolution by adversely affecting the steady-state ATP/ADP ratio and consequently the reduction of sn-phospho-3-glycerol to glyceraldehyde 3-phosphate. The results are discussed in their relation to ADP regulation of photosynthetic carbon assimilation and metabolite transport.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Oxigênio
/
Pentosefosfatos
/
Fotossíntese
/
Ribose
/
Cloroplastos
Idioma:
En
Ano de publicação:
1976
Tipo de documento:
Article