Cloning of two related genes encoding the 56-kDa and 123-kDa subunits of trehalose synthase from the yeast Saccharomyces cerevisiae.

Preparations of intact trehalose synthase contain three polypeptides with molecular masses of 56, 102 and 123 kDa. We have cloned the genes TSS1 and TSL1 coding for the 56- and 123-kDa subunits, respectively. These genes are located on chromosomes II (TSS1) and XIII (TSL1). The TSS1 gene was found to be identical with CIF1, a gene required for normal growth on glucose. The product of the entire TSS1 gene exhibits 37% identity with a 502-amino-acid stretch from the middle of the TSL1 product. Disruption of the TSS1 gene in yeast eliminates both trehalose 6-phosphate synthase (Tre6P synthase) and trehalose 6-phosphate phosphatase (Tre6Pase) activities, and reintroduction of this gene restores these activities. Transformation of Escherichia coli with TSS1 increases its Tre6P synthase activity. Specific proteolytic degradation of the 123-kDa polypeptide from the N-terminus greatly influences the Tre6P synthase activity, decreasing its inhibition by phosphate and activatability by fructose 6-phosphate but has little effect on the Tre6Pase activity. These results suggest that this N-terminal part confers regulatory properties upon the Tre6P synthase activity.