Regulation of sulphate assimilation in Saccharomyces cerevisiae.
We examined how the activity of O-acetylserine and O-acetylhomoserine sulphydrylase (OAS/OAH) SHLase of Saccharomyces cerevisiae is affected by sulphur source added to the growth medium and genetic background of the strain. In a wild-type strain, the activity was repressed if methionine, cysteine or glutathione was added to the growth medium. However, in a strain deficient of cystathionine gamma-lyase, cysteine and glutathione were repressive, but methionine was not. In strains deficient of serine O-acetyltransferase (SATase), OAS/OAH SHLase activity was low regardless of sulphur source and was further lowered by cysteine and glutathione, but not by methionine. From these observations, we concluded that S-adenosylmethionine should be excluded from being the effector for regulation of OAS/OAH SHLase. Instead, we suspected that S. cerevisiae would have the same regulatory system as Escherichia coli for sulphate assimilation; i.e. cysteine inhibits SATase to lower the cellular concentration of OAS which is required for induction of the sulphate assimilation enzymes including OAS/OAH SHLase. Subsequently, we obtained data supporting this speculation.
Laboratory of Environmental Hygiene Chemistry, Faculty of Pharmaceutical Sciences, Okayama University, Japan.
B
B
Ono
K
K
Kijima
N
N
Ishii
T
T
Kawato
A
A
Matsuda
A
A
Paszewski
S
S
Shinoda
D000123:Acetyltransferases / Q000037:antagonists & inhibitors; D019757:Carbon-Oxygen Lyases; D003545:Cysteine / Q000494:pharmacology; D003547:Cysteine Synthase; D008190:Lyases / Q000378:metabolism; D009097:Multienzyme Complexes; D012441:Saccharomyces cerevisiae / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins; D051050:Serine O-Acetyltransferase; D013431:Sulfates / Q000378:metabolism*
D009097:Multienzyme Complexes; D029701:Saccharomyces cerevisiae Proteins; D013431:Sulfates; D000123:Acetyltransferases; D051050:Serine O-Acetyltransferase; D003547:Cysteine Synthase; C103381:MET17 protein, S cerevisiae; C018725:O-acetylhomoserine (thiol)-lyase; D008190:Lyases; D019757:Carbon-Oxygen Lyases; D003545:Cysteine