UNSPECIFIED (1997) Regulation of a NAD(+) kinase activity isolated from asynchronous cultures of the achlorophyllous ZC mutant of Euglena gracilis. ZEITSCHRIFT FUR NATURFORSCHUNG C-A JOURNAL OF BIOSCIENCES, 52 (9-10). pp. 623-635. ISSN 0939-5075

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Abstract

NAD(+) kinase was isolated by chromatography steps from asynchronous cultures of the achlorophyllous ZC mutant of Euglena gracilis. A non Ca2+-calmodulin dependent form, whose activity was stimulated by EGTA, was selected for its large quantity and high specific activity. Studies of the kinetic parameters revealed two kinds of NAD(+) binding site, depending on NAD(+) concentrations, and changes induced by EGTA, Ca2+ and Ca2+-calmodulin. The search for effecters, soluble (S) and membrane-bound (P), in Euglena gracilis synchronously grown (in a light-dark regime of 12h:12h), and collected at circadian times (CT)-corresponding to the maximum, CT 17, and to the trough, CT 09, of the circadian rhythm of NAD(+) kinase activity-was also undertaken by testing the modulations of the kinetic parameters of the prepared NAD(+) kinase. The results suggest: (i) structural changes of NAD(+) binding sites depending on NAD(+) concentrations; (ii) possible binding of the Mg-ATP(-2) (or Ca-ATP(-2)) on the NAD(+) sites, because of their common ADP motif; and (iii) different and specific modulations of the kinetic parameters of the two types of NAD(+) binding site by the Ca2+-calmodulin complex. In addition, the results indicate, in pelletable fractions isolated at CT 09 and CT 17, the presence of two kinds of effector: (i) the first one, possibly Ca2+, which increases the Vmax's while decreasing the binding of NAD(+); (ii) the second one, possibly the Ca2+-calmodulin complex, which provokes a complete reverse effect. Each of these two effecters seems to be, alternatively and rhythmically (eight circadian hours apart), partially released from the membranes.

Item Type:	Journal Article
Subjects:	Q Science > QD Chemistry R Medicine > RS Pharmacy and materia medica
Journal or Publication Title:	ZEITSCHRIFT FUR NATURFORSCHUNG C-A JOURNAL OF BIOSCIENCES
Publisher:	VERLAG Z NATURFORSCH
ISSN:	0939-5075
Date:	September 1997
Volume:	52
Number:	9-10
Number of Pages:	13
Page Range:	pp. 623-635
Publication Status:	Published
URI:	http://wrap.warwick.ac.uk/id/eprint/16266

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