Stimulation of xylanase synthesis in Cryptococcus albidus by cyclic AMP

Cryptococcus albidus secretes a xylanase when induced by xylan or beta-methylxyloside, a non-metabolizable inducer, and production of the enzyme is repressed by xylose. The effect of exogenous cAMP on xylanase production was tested under different growth conditions. The cAMP elicited a 1.5 to 2 fold increase in xylanase production during the induction by xylan and B-methylxyloside but did not relieve the repression observed during growth on xylose. Cyclic AMP also affected the growth rate of the cells and did not modulate the activity of pure xylanase in vitro. A 15-nucleotide sequence located upstream from the xylanase gene could be part of a cAMP regulatory sequence.