Biology

Glutamine synthetase in marine algae: New surprises from an old enzyme

Document Type

Article

Abstract

Glutamine synthetase (GS), which catalyzes the formation of glutamine from ammonium and glutamate in the presence of ATP, is encoded by three distinct gene families: GSI, GSII, and GSIII. Genes encoding GSI are found in the Bacteria and Archaea, whereas GSII genes are found in eukaryotes and a few species of Bacteria. Members of the third family, GSIII, have been described from a limited number of bacteria; however, recent biochemical and molecular data suggest that this type of enzyme is broadly distributed among the algae. Peptide fragments obtained from GS purified from the marine diatom Skeletonema costatum (Greville) Cleve are 77% identical to a partial sequence of GSIII from Chaetoceros compressum Lauder, which permits the unambiguous assignment of the biochemically characterized enzyme to the GSIII gene family. The N-terminal sequence was 43% identical to the GSIII-like enzyme purified from the haptophyte Emiliania huxleyi (Lohm.) Hay et Miller and several residues were conserved among bacterial and eukaryotic GSIII enzymes. The presence of genes encoding GSIII in diatoms and haptophytes indicates that this enzyme family is more broadly distributed in eukaryotes than previously suspected.

Publication Title

Journal of Phycology

Publication Date

11-12-2001

Volume

37

Issue

5

First Page

793

Last Page

795

ISSN

0022-3646

DOI

10.1046/j.1529-8817.2001.01057.x

Keywords

Diatoms, evolution, Glutamine synthetase, Nitrogen metabolism, Skeletonema costatum

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