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Zur Regulation der NADP-abhängigen Glycerinaldehyd-3-phosphat-Dehydrogenase in den Primärblättern von Phaseolus vulgaris L.

1974; Elsevier BV; Volume: 166; Issue: 5-6 Linguagem: Inglês

10.1016/s0015-3796(17)30088-4

0015-3796

Zsuzsanna Schwarz,

Photosynthetic Processes and Mechanisms

Addition of Na-cholate to the homogenizing buffer during and after homogenization causes an increase of activity of the NADP-GAPD (E. C. 1.2.1.13) in crude extracts of primary leaves of Phaseolus vulgaris. This effect seems to be based on the activation of an (in vivo) inactive enzyme and have been discussed as a reversible binding (= inactivation) of the enzyme to chloroplast structures. The extent of the increase of enzyme activity by cholate is related to the function of the photosynthetic apparatus: The highest portion of “inactive” enzyme (becoming active only after addition of cholate in vitro) could be detected in primary leaves of young plants. After dark and light transients of green plants the relation between “active” and “inactive” NADP-GAPDH enzyme molecules is constant, even after treatment with chloramphenicol. Consequently, neither the decrease of activity in darkness nor the increase of activity after exposure to light can be the result of a de novo synthesis of enzyme protein. Our results on the regulation of the NADP-GAPDH having been obtained in crude extracts may be discussed rather in relation to reversible changes of plastid-structures than in regard to an allosteric control of the enzyme.