Evidence for the existence of two soluble NAD+ kinase isoenzymes in Euglena gracilis Z

11Citations
Citations of this article
8Readers
Mendeley users who have this article in their library.
Get full text

Abstract

Two soluble NAD+ kinase isoenzymes (isoenzymes 1 and 2) from Euglena gracilis were separated by preparative electrophoresis and characterized. They display several similar properties: both have an identical apparent molecular weight of 68 kDa and their activities are independent on calmodulin, insensitive to 2-mercaptoethanol but inhibited by p- chloromercurybenzoate, 5,5'-dithiobis(2-nitrobenzoate) and, surprisingly, by low dithiothreitol concentrations, the inhibition by dithiothreitol being irreversible for isoenzyme 1 but reversible for isoenzyme 2. Nevertheless, the two isoenzymes mainly differ by their specificities towards triphosphate nucleotides and their catalytic mechanisms. Isoenzyme 1 is as active in the presence of ATP as of GTP and acts by a ping-pong mechanism with a k(M) for NAD+ of 0.26 mM and a k(M) for low MgATP2-concentrations of 0.03 mM. Isoenzyme 2 is three-fold more active in the presence of GTP than of ATP and operates by a sequential mechanism with k(M)s for NAD+ and MgGTP2- of 1.03 and 0.20 mM, respectively. This study shows the evidence for the existence of two structurally similar but catalytically different NAD+ kinase isoenzymes in E. gracilis. One resembles the enzyme previously described in bacteria. The other displays a catalytic mechanism identical to that of NAD+ kinase from other organisms but remains unique among all the NAD+ kinases studied to-date regarding its specificity towards GTP. © 2000 Elsevier Science Ltd.

Cite

CITATION STYLE

APA

Stephan, C., Renard, M., & Montrichard, F. (2000). Evidence for the existence of two soluble NAD+ kinase isoenzymes in Euglena gracilis Z. International Journal of Biochemistry and Cell Biology, 32(8), 855–863. https://doi.org/10.1016/S1357-2725(00)00032-7

Register to see more suggestions

Mendeley helps you to discover research relevant for your work.

Already have an account?

Save time finding and organizing research with Mendeley

Sign up for free