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. Sulfur deficiency increased the activity of the sulfur assimilation enzyme O-acetyl serine sulfhydrylase but decreased the MTHB S-methyltransferase activity. 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 results will be discussed in relation to the regulation of biosynthesis of DMSP.
