Peroxisomes are required for efficient penicillin biosynthesis in Penicillium chrysogenum.

In the fungus Penicillium chrysogenum, penicillin (PEN) production is compartmentalized in the cytosol and in peroxisomes. Here we show that intact peroxisomes that contain the two final enzymes of PEN biosynthesis, acyl coenzyme A (CoA):6-amino penicillanic acid acyltransferase (AT) as well as the side-chain precursor activation enzyme phenylacetyl CoA ligase (PCL), are crucial for efficient PEN synthesis. Moreover, increasing PEN titers are associated with increasing peroxisome numbers.

Physiological and transcriptional characterization of Saccharomyces cerevisiae strains with modified expression of catabolic regulators.

A comparative physiological and transcriptional study is presented on wild-type Saccharomyces cerevisiae and mutants with altered levels of catabolic regulators: hxk2Delta lacking hexokinase2, HAP4 / overproducing hap4p and hxk2 Delta HAP4 upward arrow. Relative to the wild-type, HAP4 / showed the same growth rate with some increased yield on glucose, and hxk2Delta grew 28% slower but with a dramatically improved yield. Hxk2 Delta HAP4 / grew 14% slower but showed fully oxidative growth.

Overexpression of HAP4 in glucose-derepressed yeast cells reveals respiratory control of glucose-regulated genes.

A link between control of respiration and glucose repression in yeast is reported. The HAP4 gene was overexpressed in a Delta mig1 deletion background, generating a mutant in which respiratory function is stimulated and glucose repression is diminished. Although this combination does not result in derepression of genes encoding proteins involved in respiratory function, it nevertheless generates resistance against 2-deoxyglucose and hence contributes to more derepressed growth characteristics.

Quantitative comparison of cDNA-AFLP, microarrays, and GeneChip expression data in Saccharomyces cerevisiae.

cDNA-AFLP is a genome-wide expression analysis technology that does not require any prior knowledge of gene sequences. This PCR-based technique combines a high sensitivity with a high specificity, allowing detection of rarely expressed genes and distinguishing between homologous genes. In this report, we validated quantitative expression data of 110 cDNA-AFLP fragments in yeast with DNA microarrays and GeneChip data.

Hap4p overexpression in glucose-grown Saccharomyces cerevisiae induces cells to enter a novel metabolic state.

Background: Metabolic and regulatory gene networks generally tend to be stable. However, we have recently shown that overexpression of the transcriptional activator Hap4p in yeast causes cells to move to a state characterized by increased respiratory activity. To understand why overexpression of HAP4 is able to override the signals that normally result in glucose repression of mitochondrial function, we analyzed in detail the changes that occur in these cells.