Purification and characterization of secreted acid phosphatase under phosphate-deficient condition in Pholiota nameko

Purification, characterization, and gene cloning of glucose-1-phosphatase from Citrobacter braakii

Citrobacter braakii produced an intracellular acid glucose phosphatase (AgpC) which was purified 986 fold to homogeneity with the specific activity of 286 units/mg. AgpC hydrolyzed a wide variety of phosphorylated compounds with high activity for glucose-1-phosphate and glucose-6-phosphate. The optimum pH and temperature for the enzyme activity was pH 5.0 and 45 degrees C, respectively. The Km value for glucose-1-phosphate was 5.12 mM with a Vmax 27.8 U mg(-1). Its molecular weight was 46 kDa by SDS-PAGE gel and the sequence of N-terminal amino acid residues identified was Gln-Thr-Ala-Pro-Glu-Gly-Tyr-Gln-Leu-Gln. The glucose-1-phosphatase gene (agpC) was cloned from the C. braakii genomic library. This gene comprised 1,242 nucleotides and encoded a polypeptide of 413 amino acids. The result of its BLAST search showed a significant similarity with glucose-1-phosphatase from enterobacteria such as E. coli, Enterobacter, Shigella, and Salmonella.

Structure and expression of two genes encoding secreted acid phosphatases under phosphate-deficient conditions in Pholiota nameko strain N2

Twenty-three polypeptides secreted in response to a deficiency of inorganic phosphate (Pi) were previously found by two-dimensional polyacrylamide gel electrophoresis analysis in mycelia of Pholiota nameko strain N2. In this study, N-terminal sequencing revealed three of them to be identical to known acid phosphatases of P. nameko strain N114. Two cDNAs and the corresponding genomic DNAs of genes PNAP1 and PNAP2 which encode two of the three acid phosphatases were cloned. The deduced amino acid sequences of PNAP1 and PNAP2 showed high similarity to other fungal acid phosphatases and contained a putative catalytic active site of acid phosphatase. PNAP1 and PNAP2 are comprised of five and seven exons interrupted by four and six introns, respectively. Their promoter regions include two cis-acting elements found in Pi deficiency-inducible genes of Saccharomyces cerevisiae, together with several known functional elements such as a TATA box. Northern blot analysis showed that PNAP1 and PNAP2 are expressed in response to a deficiency of Pi.

Gene expression during Pi deficiency in Pholiota nameko: accumulation of mRNAs for two transporters

The effects of Pi deficiency on gene expression in Pholiota nameko were examined. A cDNA library was constructed from poly(A)+ RNA isolated from mycelia cultured in Pi-depleted (P-) media, and 150 clones corresponding to Pi deficiency-inducible (pdi) genes were selected by differential hybridization with probes prepared from poly(A)+ RNAs from the mycelia cultured in the Pi-supplied (P+) and P- media. These clones were considered to derive from 31 genes by cross-hybridization. Northern blot analysis showed that these pdi genes were expressed in various patterns during Pi deficiency. Among the clones, the DNA sequences of pdi85 and pdi343 were analyzed. The deduced amino acid sequences indicated that they have structural similarities to Pi and metabolite transporters.