Identification and stereospecificity of the first three enzymes of 3-dimethylsulfoniopropionate biosynthesis in a chlorophyte alga

Peter S. Summers, Kurt D Nolte, Arthur J L Cooper, Heidi Borgeas, Thomas Leustek, David Rhodes, Andrew D. Hanson

Research output: Contribution to journalArticle

39 Citations (Scopus)

Abstract

Many marine algae produce 3-dimethylsulfoniopropionate (DMSP), a potent osmoprotective compound whose degradation product dimethylsulfide plays a central role in the biogeochemical S cycle. Algae are known to synthesize DMSP via the four-step pathway, L-Met → 4-methylthio-2-oxobutyrate → 4-methylthio-2-hydroxybutyrate → 4-dimethylsulfonio-2-hydroxy-butyrate (DMSHB) → DMSP. Substrate-specific enzymes catalyzing the first three steps in this pathway were detected and partially characterized in cell-free extracts of the chlorophyte alga Enteromorpha intestinalis. The first is a 2-oxoglutarate-dependent aminotransferase, the second an NADPH-linked reductase, and the third an S-adenosylmethionine-dependent methyltransferase. Sensitive radiometric assays were developed for these enzymes, and used to show that their activities are high enough to account for the estimated in vivo flux from Met to DMSP. The activities of these enzymes in other DMSP-rich chlorophyte algae were at least as high as those in E. intestinalis, but were ≥20-fold lower in algae without DMSP. The reductase and methyltransferase were specific for the D-enantiomer of 4-methylthio-2-hydroxybutyrate in vitro, and both the methyltransferase step and the step(s) converting DMSHB to DMSP were shown to prefer D-enantiomers in vivo. The intermediate DMSHB was shown to act as an osmoprotectant, which indicates that the first three steps of the DMSP synthesis pathway may be sufficient to confer osmotolerance.

Original languageEnglish (US)
Pages (from-to)369-378
Number of pages10
JournalPlant Physiology
Volume116
Issue number1
StatePublished - 1998
Externally publishedYes

Fingerprint

algae
biosynthesis
Enzymes
enzymes
Butyrates
methyltransferases
Methyltransferases
butyrates
osmotolerance
enantiomers
Oxidoreductases
S-Adenosylmethionine
S-adenosylmethionine
dimethylsulfoniopropionate
dimethylpropiothetin
Ulva
transaminases
Transaminases
Cell Extracts
NADP

ASJC Scopus subject areas

  • Plant Science

Cite this

Summers, P. S., Nolte, K. D., Cooper, A. J. L., Borgeas, H., Leustek, T., Rhodes, D., & Hanson, A. D. (1998). Identification and stereospecificity of the first three enzymes of 3-dimethylsulfoniopropionate biosynthesis in a chlorophyte alga. Plant Physiology, 116(1), 369-378.

Identification and stereospecificity of the first three enzymes of 3-dimethylsulfoniopropionate biosynthesis in a chlorophyte alga. / Summers, Peter S.; Nolte, Kurt D; Cooper, Arthur J L; Borgeas, Heidi; Leustek, Thomas; Rhodes, David; Hanson, Andrew D.

In: Plant Physiology, Vol. 116, No. 1, 1998, p. 369-378.

Research output: Contribution to journalArticle

Summers, PS, Nolte, KD, Cooper, AJL, Borgeas, H, Leustek, T, Rhodes, D & Hanson, AD 1998, 'Identification and stereospecificity of the first three enzymes of 3-dimethylsulfoniopropionate biosynthesis in a chlorophyte alga', Plant Physiology, vol. 116, no. 1, pp. 369-378.
Summers, Peter S. ; Nolte, Kurt D ; Cooper, Arthur J L ; Borgeas, Heidi ; Leustek, Thomas ; Rhodes, David ; Hanson, Andrew D. / Identification and stereospecificity of the first three enzymes of 3-dimethylsulfoniopropionate biosynthesis in a chlorophyte alga. In: Plant Physiology. 1998 ; Vol. 116, No. 1. pp. 369-378.
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