ABSTRACT. The present study was designed to identify alkaline phosphatases in non-permeabilized hyphal cells of the fungus Neurospora crassa by staining these enzymatic activities with a modified azo dye coupling method. Our strategy allowed the identification of three non-specific alkaline phosphatase activities, one of them possibly being a novel putative enzyme, which is not responsive to either Mg²⁺ or EDTA. Another alkaline phosphatase activity, whose location in the hyphal cell is regulated by phosphate, is stimulated by Mg²⁺, inhibited by EDTA, and somehow dependent on the expression of the pho-2⁺-encoded Pi-repressible alkaline phosphatase.

Key words: Alkaline phosphatase, Gene regulation, Neurospora crassa, Phosphate sensing