Further studies on the multiple forms of protease ALP of Aspergillus fumigatus

The author studied the presence of multiple forms of the main extracellular protease ALP in three strains of Aspergillus fumigatus that differed in geographical origin, and in mutants of one of these strains with disrupted genes coding for the main proteases ALP and MEP. The pattern of multiple proteolytic bands after isoelectric focusing was, in all three wild strains, nearly the same and was not changed after inactivation of the MEP gene. However, in ALP-deficient mutants all multiple forms also disappeared. The multiple forms observed must therefore be products of post-translational processing of the protease ALP and not true isoenzymes (products of different genes of a gene family). Further experiments did not prove that phosphorylation and glycosylation were involved in the formation of the multiple forms under study.