title: REGULATION OF BIOSYNTHESIS OF DIMETHYLSULFONIOPROPIONATE AND ITS UPTAKE IN STERILE MUTANT OF ULVA PERTUSA (CHLOROPHYTA)1.
abstract: It has been shown that marine algae produce the compatible solute dimethylsulfoniopropionate (DMSP) from methionine (Met) via four enzymatic reactions in which the third step, synthesis of 4-dimethylsulfonio-2-hydroxy-butyrate (DMSHB) from 4-methylthio-2-hydroxybutyrate (MTHB), is the committing step. However, regulation of the biosynthetic pathways and transport properties of DMSP is largely unknown. Here, the effects of sulfur and sodium concentrations on the uptake and synthesis of DMSHB and DMSP were examined in a sterile mutant of Ulva pertusa Kjellm. Sulfur deficiency increased the activity of the sulfur assimilation enzyme O-acetyl serine sulfhydrylase but decreased the MTHB S-methyltransferase activity, suggesting the preferential utilization of sulfur atoms for Met metabolites other than DMSP. Uptake of DMSP and DMSHB was enhanced by S deficiency. High salinity enhanced the MTHB S-methyltransferase activity as well as the uptake of DMSHB. The MTHB S-methyltransferase activity was inhibited by its product DMSP. These data demonstrate the importance of MTHB S-methyltransferase activity and uptake of DMSHB for the regulation of DMSP.
authors.affiliation: Graduate School of Environmental, Human Sciences, Meijo University, Nagoya 468-8502, JapanResearch Institute, Meijo University, Nagoya 468-8502, Japan.
authors.forename: Takayuki
authors.initials: T
authors.lastname: Ito
authors.affiliation: Graduate School of Environmental, Human Sciences, Meijo University, Nagoya 468-8502, JapanResearch Institute, Meijo University, Nagoya 468-8502, Japan.
authors.forename: Yugo
authors.initials: Y
authors.lastname: Asano
authors.affiliation: Graduate School of Environmental, Human Sciences, Meijo University, Nagoya 468-8502, JapanResearch Institute, Meijo University, Nagoya 468-8502, Japan.
authors.forename: Yoshito
authors.initials: Y
authors.lastname: Tanaka
authors.affiliation: Graduate School of Environmental, Human Sciences, Meijo University, Nagoya 468-8502, JapanResearch Institute, Meijo University, Nagoya 468-8502, Japan.
authors.forename: Teruhiro
authors.initials: T
authors.lastname: Takabe
keywords: DMSP; Ulva; green algae; salt stress; sulfur deficiency