Format

Send to

Choose Destination
See comment in PubMed Commons below
Biofactors. 1999;10(2-3):237-44.

Biosynthesis of selenophosphate.

Author information

1
Laboratory of Biochemistry, National Heart, Lung, Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.

Abstract

Selenophosphate synthetase, the product of the selD gene, produces the highly active selenium donor, monoselenophosphate, from selenide and ATP. Positional isotope exchange experiments have shown hydrolysis of ATP occurs by way of a phosphoryl-enzyme intermediate. Although, mutagenesis studies have demonstrated Cys17 in the Escherichia coli enzyme is essential for catalytic activity the nucleophile in catalysis has not been identified. Recently, selenophosphate synthetase enzymes have been identified from other organisms. The human enzyme which contains a threonine residue corresponding to Cys17 in the E. coli enzyme, has been overexpressed in E. coli. The purified enzyme shows no detectable activity in the in vitro selenophosphate synthetase assay. In contrast, when the human enzyme is expressed to complement a selD mutation in E. coli, in the presence of 75Se, incorporation of 75Se into bacterial selenoproteins is observed. The inactive purified human enzyme together with the very low determined specific activity of the E. coli enzyme (83 nmol/min/mg) suggest an essential component for the formation of selenophosphate has not been identified.

PMID:
10609888
[Indexed for MEDLINE]
PubMed Commons home

PubMed Commons

0 comments
How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Wiley
    Loading ...
    Support Center