Glucose-repression

Yeasts contain a large number of different active and passive sugar-transport systems. The first of these to be cloned was the glucose-repressible, high-affinity passive glucose transporter of Saccharomyces cerevisiae, which is encoded by the SNF3 gene... 

Glucose represses gene expression by lowering the level of cAMP in the cell, thus preventing the cAMP-dependent activator binding to the CAP-site sequence. 

Regulation of catalase expression in eukaryotes takes place as part of a generalized response mechanism. In yeast, promoter elements of the peroxisomal catalase CTA-1 respond to glucose repression and activation by fatty acids as part of organelle synthesis. The cytosolic catalase CTT-1 responds as part of a generalized stress response to starvation, heat, high osmolarity, and H2O2, and there is even evidence of translational control mediated by heme availability 26). 

Langsford et al. reported that Cellulomonas fimi culture supernatants contained cellulase and proteinase activities, for which there appeared to be a relationship. Glucose repressed the synthesis of both activities and cellulose induced both 60), Adding cellulose to Cellulomonas sp. (NRCC 2406) cultures stimulated growth and improved production of cellulases 61). Optimum conditions for growth and cellulase production were pH 6.5 and 30 C. The addition of glucose in the presence of cellulose inhibited growth. Several species of Cellulomonas have cellobiose phosphorylase. 

Escalante L, Ramos I, Imriskova I, Langley E, Sanchez S. (1999) Glucose repression of anthracycline formation in Streptomyces peucetius var. caesius. Appl Microbiol Biotechnol 52 572-578. 

Kim E-S, Hong H-J, Choi C-Y, Cohen SN, Modulation of actinorhodin biosynthesis in Streptomyces lividans by glucose repression of afsR2 gene transcription,... 

When suitable strains to exploit natural substrates are available, their exploitation of cellulolytic substrates in pure culture could be restricted by the end-products of cellulolysis (cellobiose and glucose) repressing enzyme synthesis or inhibition/inactivation of further enzymic activity (Fig. 1). One of the simplest routes to relieve this difficulty was to use non-celluloly tic... 

Babczinski and Tanner,S3 have reported an additional isoenzyme of /3-D-fructofuranosidase which they considered to be a precursor of the main enzyme. This new enzyme is associated with crude, membrane fractions of the cells it has a molecular weight of 190,000, and appears transiently, as < 5% of the total /3-D-fructofuranosidase, when the yeast is actively synthesizing the external enzyme. From studies on the effects of D-glucose repression and of cycloheximide, Sentandreu and coworkers (see Ref. 154) also considered that such an enzyme, associated more with internal membranes than with plasmalemma, might be, at least in part, a precursor of the external /3-D-fructofuranosidase in the process of secretion. 

Although the S. cerevisiae MT gene is also glucose-repressible (see Butt Ecker, 1987), the primary role of this protein appears to be in metal homeostasis. This conclusion must also be drawn for the N. crassa MT, the expression of which does not appear to be regulated by anything other than Cu (Munger et al., 1987). 

The yeast growth is diauxic 17). Under the conditions of glucose repression, ethanol formation takes place even in the presence of oxygen. Yeasts require a small but finite oxygen supply for synthesis of unsaturated fatty acids, sterols, and nicotinic acid. These compounds which are essential to membrane functions are synthesized only aerobically 18). 

Carlson, M., 1999, Glucose repression in yeast. Curr. Opin. Microbiol. 2 202-207. 

Meijer, M.M.C., Boonstra, J., Verkleij, A.J., Veriips, C.T. (1998) Glucose repression in Saccharomyces cerevisiae is related to the glucose concentration rather than the glucose flux. J. Biol. Chem., 273, 24102-24107. 

Cho, J.H., Lee, Y.K. and Chae, C.B. (2001) The modulation of the biological activities of mitochondrial histone Abf2p by yeast PKA and its possible role in the regulation of mitochondrial DNA content during glucose repression. Biochim. Biophys. Acta 1522, 175-186. 

Fig. 4. Dimerization and phosphorylation of Hxk2. Hexokinase PII (Hxk2) was one of the first proteins to be implicated in glucose repression and adaptation to fermentative metabolism. However, its role is still unclear. Hxk2 is a phosphoprotein which exists in a mono- or dimeric state. Only the monomer is phosphorylated. Hxk2 is found in the cytoplasm and the nucleus which suggests that it may play roles in both hexose metabolism and transcriptional regulation [76,77]...

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