Purification and properties of two isozymes of pyruvate kinase from Mucor racemosus

Abstract

The dimorphic phycomycete Mucor racemosus was found to contain up (7,13).In each of these systems the isozyme types could be generated in a variety of different ways, including multiple structural genes for pyruvate kinase, posttranscriptional modification of transcripts from a single gene, and posttranslational modification of the product from a single transcript.We report here on the purification and characterization of two forms of M. racemosus pyruvate kinase, PK1 and PK5, and provide evidence that these electrophoretic forms are isozymic homotetramers composed of unique subunits. MATERIALS AND METHODSOrganism and growth conditions. M. racemosus ATCC 1216B was grown in 10-liter carboys continuously sparged with either air (PK1) or CO2 (PK5) and incubated at room temperature (20 to 23°C). For PK1, the organism was grown on a defined medium containing 0.5% glutamate and adjusted to pH 5.0 with H2SO4. These

Mucor dimorphism.

“…The same isozymes of pyruvate kinase are also demonstrable in extracts of M. racemosus (170). They most likely represent separate gene products (98); however, the differential expression observed in yeasts and hyphae is not related to morphogenesis but simply to glucose repression under anaerobiosis (170). Phosphofructokinase occurs at levels 30 to 40 times higher in extracts of anaerobic yeasts than in extracts of aerobic hyphae of M. rouxii.…”

Intermediary Metabolism

“…The enzyme was shown to have hyperbolic kinetics towards (Yeung and Kapoor, 1983) and S. cerevisiae (Morris et al, 1984), the Deuteromycete Aspergillus niger (Meixner-Monori et al, 1984) as well as the Zygomycetes P. blakesleeanus (De Arriaga et al, 1989), M. rouxii (Passeron and Roselino, 1971) and Mucor racemosus (Hohn and Paznokas, 1987). The P. blakesleeanus enzyme is inhibited by alanine and by high ATP concentrations (De Arriaga et al, 1989).…”

“…In Coprinus lagopus pyruvate kinase is also highly regulated (Stewart and Moore, 1971). Different isoenzymes, one of them only poorly stimulated by fructose I, 6-bisphosphate, have only been described in the Mucor species and their expression depends on culture conditions (Hohn and Paznokas, 1987).…”