Physiological control of repressible acid phosphatase gene transcripts in Saccharomyces cerevisiae.

Abstract

We have examined the regulation of repressible acid phosphatase (APase; orthophosphoric-monoester phosphohydrolase [ Phosphorus metabolism in Saccharomyces cerevisiae involves five principal enzymes for the acquisition and metabolic integration of Pi.These enzymes regulate intracellular concentrations of Pi by a cyclic pathway of polyphosphate (polyP) synthesis and degradation (18, 47). The polyP is sequestered into vacuoles and forms the most abundant phosphate compounds in yeasts. The majority is an acid-insoluble polymer of 240,000 daltons, whereas the remainder consists of short-chain-length acid-soluble residues (42).Both a phosphate permease (39) and acid phosphatase (APase) (41) participate in phosphorus acquisition. APase (orthophosphoricmonoester phosphohydrolase [acid optimum], EC 3.1.3.2) is an exocellular enzyme active on a broad spectrum of phosphoester substrates (41).Incorporation of Pi as a monovalent anion occurs by an energy-dependent permease transport mechanism (9, 39). Intracellular Pi is converted via ATP to polyP by the unique enzyme, polyP kinase, which transfers the terminal phosphoryl group of ATP to polyP. Degradation of polyP, on the other hand, is catalyzed by several enzymes, including polyP kinase. However, the direct interconversion of polyP to ATP by polyP kinase does not occur in vivo. Rather, polyP is sequentially hydrolyzed to smaller-chain-length

Regulation of repressible acid phosphatase gene transcription in Saccharomyces cerevisiae.

“…Under derepressed conditions, the PHO81 product binds to the PHO80, PHO85,PH04 aggregate, and the PH04 product is released. It binds, with the PHO2 protein, to an operator of the structural gene and activates transcription.Considerable biochemical and molecular evidence (5,6,11,17) indicates transcriptional regulation of APase and AlkPase. Three distinct APase polypeptides (p60, p58, and 2131 on May 11, 2018 by guest…”

“…Considerable biochemical and molecular evidence (5,6,11,17) indicates transcriptional regulation of APase and AlkPase. Three distinct APase polypeptides (p60, p58, and 2131 on May 11, 2018 by guest…”

“…These enzymes regulate intracellular concentrations of Pi and maintain cellular homeostasis (7, 8) by a cyclic pathway of polyphosphate synthesis and degradation (7). They are themselves regulated by external growth concentrations of Pi (6,7,9,10).This family of enzymes is a dispersed system composed of numerous structural and regulatory genes (Table 1). There are four known structural genes encoding APase (PHO3, PHO5, PHOJO, PHOII), genes for AlkPase (PHO8) and Pi transport (PHO84), and eight genes affecting their expression (9, 23-28).…”

“…b The designation constitutive for PH03 is qualified because its expression is significantly lowered when PHOS is derepressed (17). p56) encoded by three repressible APase mRNAs are the products of the PHO5, PHOJO, and PHOIJ genes, respectively (5,6). Derepression results from a cellular increase in all three mRNAs and subsequent de novo enzyme synthesis.…”

“…These enzymes regulate intracellular concentrations of Pi and maintain cellular homeostasis (7, 8) by a cyclic pathway of polyphosphate synthesis and degradation (7). They are themselves regulated by external growth concentrations of Pi (6,7,9,10).…”