Capacity for NADPH/NADP turnover in the cytosol of barley seed endosperm: The role of NADPH-dependent hydroxypyruvate reductase
2000 (English)In: Plant physiology and biochemistry (Paris), ISSN 0981-9428, Vol. 38, no 10, 747-753 p.Article in journal (Refereed) Published
Barley (Hordeum vulgare L.) endosperm from developing seeds was found to contain relatively high activities of cytosolic NAD(P)II-dependent hydroxypyruvate reductase (HPR-2) and isocitrate dehydrogenase (ICDH). In contrast, activities of peroxisomal NADH-dependent hydroxypyruvate reductase (HPR-1) and glycolate oxidase as well as cytosolic NAD(P)H-dependent glyoxylate reductase were very low or absent in the endosperm both during maturation and seed germination, indicating the lack of a complete glycolate cycle in this tissue. In addition, activities of cytosolic glucose-6-phosphate dehydrogenase and glyceraldehyde-3-phosphate dehydrogenase were low or absent in the endosperm. The endosperm HPR-2 exhibited similar properties to those of an earlier described HPR-2 from green leaves, e.g. activities with both hydroxypyruvate and glyoxylate, utilization of both NADPH and NADH as cofactors, and a strong uncompetitive inhibition by oxalate (K-i in the order of micromolar). In etiolated leaves, both HPR-1 and HPR-2 were present with the same activity as in green leaves, indicating that the lack of HPR-I in the endosperm is not a general feature of non-photosynthetic tissues. We conclude that the endosperm has considerable capacity for cytosolic NADP/NADPH cycling via HPR-2 and ICDH, the former being possibly involved in the utilization of a serine-derived carbon. (C) 2000 Editions scientifiques et medicales Elsevier SAS.
Place, publisher, year, edition, pages
2000. Vol. 38, no 10, 747-753 p.
cytosol, glyoxylate, Hordeum vulgare, hydroxypyruvate reductase, seed germination, starch synthesis, sucrose synthesis
IdentifiersURN: urn:nbn:se:umu:diva-44737ISI: 000165402300003OAI: oai:DiVA.org:umu-44737DiVA: diva2:426355