Characterization of the 56-kDa subunit of yeast trehalose-6-phosphate synthase and cloning of its gene reveal its identity with the product of CIF1, a regulator of carbon catabolite inactivation.
Trehalose-6-phosphate synthase is the key enzyme for biosynthesis of trehalose, the major soluble carbohydrate in resting cells of yeast. This enzyme was purified from a strain of Saccharomyces cerevisiae lacking vacuolar proteases. It was found to be a multimeric protein of 630 kDa. Monoclonal antibodies were raised against its smallest subunit (56 kDa) and used for screening a yeast cDNA library. This yielded an immunopositive cDNA clone of 1.7 kb, containing an open reading frame of 1485 base pairs. Its sequence, called TPS1 (for trehalose-6-phosphate synthase), was represented by a single gene in the yeast genome and was found to be almost identical with the recently sequenced CIF1, a gene important for carbon catabolite inactivation, believed to be allelic with FDP1. A mutant obtained by disruption of TPS1 had a very low activity of trehalose-6-phosphate synthase, indicating that TPS1 is an important component of the enzyme. The mutant also showed a growth defect when transferred from glycerol to glucose, a phenotype similar to that of the cif1 and fdp1 mutants deficient in carbon catabolite inactivation. Thus, the smallest subunit of the biosynthetic enzyme trehalose-6-phosphate synthase appears to have, in addition, a central regulatory role in the carbohydrate metabolism of yeast.
Bell
W
W
Botanisches Institut, Universität Basel, Switzerland.
Klaassen
P
P
Ohnacker
M
M
Boller
T
T
Herweijer
M
M
Schoppink
P
P
Van der Zee
P
P
Wiemken
A
A
D000595:Amino Acid Sequence; D001483:Base Sequence; D015139:Blotting, Southern; D002244:Carbon / Q000378:metabolism*; D003001:Cloning, Molecular; D004271:DNA, Fungal; D004591:Electrophoresis, Polyacrylamide Gel; D005964:Glucosyltransferases / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics
D004271:DNA, Fungal; D002244:Carbon; D005964:Glucosyltransferases; C023180:trehalose-6-phosphate synthase