Changes in activities of the embden-meyerhof-parnas and pentose phosphate pathways during the growth cycle of Aspergillus niger

Abstract

The specific activities of certain enzymes of the Embden-Meyerhof-Parnas (EMP) and pentose phosphate (PP) pathways varied in cultures of Aspergillus niger in relation to the stage of the growth cycle and the nature of the growth medium. At 24 h from spore inoculation the levels of PP pathway enzymes glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and transketolase were higher in extracts from non-sporulating than from sporulating mycelium. Correspondingly, the levels of most EMP pathway enzymes were higher in extracts from sporulating than from non-sporulating mycelium. These fluctuations in enzyme levels occurred well in advance of any morphological evidence of sporulation. At later stages of growth (48–96 h) the levels of the enzymes were similar in extracts from both types of mycelium. Radiorespirometric patterns for the oxidation of specifically labelled [14C] glucose implied that the EMP and PP pathways were active in both types of mycelium. The contribution of the PP pathway was highest in young non-sporulating mycelium whereas the contribution of the EMP pathway was highest in sporulating mycelium of corresponding age.