Plant glycerol-3-phosphate-1-acyltransferase (GPAT): structure selectivitystudies

Squash glycerol-3-phospate-1-acyltransferase has been crystallized and the structure of the enzyme determined, at 1.9-Angstrom resolution, using multi ple isomorphous replacement of the wild type and a series of individual cys teine mutants. Competitive in vitro substrate selectivity assays have been established that differentiate between selective and non-selective forms of the enzyme, Particular care was taken to use near-physiological concentrat ions of both substrates. Clear substrate selectivity can be demonstrated wi th the natural substrate acyl-acyl carrier protein but not with the substra te analogue acyl-CoA. The use of site-directed mutagenesis, coupled to thre e-dimensional structural determinations, should provide a rational basis fo r elucidating structural components important in determining the substrate selectivity of this enzyme,