Regulation of formation of the intracellular beta-galactosidase activity of Aspergillus nidulans.
The regulation of formation of the single intracellular beta-galactosidase activity of Aspergillus nidulans was investigated. beta-Galactosidase was not formed during growth on glucose or glycerol, but was rapidly induced during growth on lactose or D-galactose. L-Arabinose, and -- with lower efficacy -- D-xylose also induced beta-galactosidase activity. Addition of glucose to cultures growing on lactose led to a rapid decrease in beta-galactosidase activity. In contrast, in cultures growing on D-galactose, addition of glucose decreased the activity of beta-galactosidase only slightly. Glucose inhibited the uptake of lactose, but not of D-galactose, and required the carbon catabolite repressor CreA for this. In addition, CreA also repressed the formation of basal levels of beta-galactosidase and partially interfered with the induction of beta-galactosidase by D-galactose, L-arabinose, and D-xylose. D-Galactose phosphorylation was not necessary for beta-galactosidase induction, since induction by D-galactose occurred in an A. nidulans mutant defective in galactose kinase, and by the non-metabolizable D-galactose analogue fucose in the wild-type strain. Interestingly, a mutant in galactose-1-phosphate uridylyl transferase produced beta-galactosidase at a low, constitutive level even on glucose and glycerol and was no longer inducible by D-galactose, whereas it was still inducible by L-arabinose. We conclude that biosynthesis of the intracellular beta-galactosidase of A. nidulans is regulated by CreA, partially repressed by galactose-1-phosphate uridylyl transferase, and induced by D-galactose and L-arabinose in independent ways.
Fekete
Erzsébet
E
Department of Microbiology and Biotechnology, Faculty of Science, University of Debrecen, 4010, P.O.Box 63, Debrecen, Hungary.
Karaffa
Levente
L
Sándor
Erzsébet
E
Seiboth
Bernhard
B
Biró
Sándor
S
Szentirmai
Attila
A
Kubicek
Christian P
CP
D001233:Aspergillus nidulans / Q000166:cytology / Q000201:enzymology* / Q000378:metabolism; D005690:Galactose / Q000819:agonists / Q000378:metabolism; D005947:Glucose / Q000037:antagonists & inhibitors / Q000378:metabolism; D005990:Glycerol / Q000378:metabolism; D007716:Kluyveromyces / Q000378:metabolism; D007785:Lactose / Q000378:metabolism; D009154:Mutation; D011134:Polysaccharides / Q000819:agonists / Q000145:classification / Q000378:metabolism; D001616:beta-Galactosidase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*
D011134:Polysaccharides; C007916:hemicellulose; D001616:beta-Galactosidase; D005947:Glucose; D007785:Lactose; D005990:Glycerol; D005690:Galactose