10.10 Phosphatases and sulfatases

Phosphatases are also esterases, acting on esters of alcohols with phosphoric and sulfuric acids. They are enzymes of comparatively low specificity but fall into groups depending on their activity as phosphomonoesterases, phosphodiesterases and polyphosphatases. The phosphomonoesterases are further distinguished according to their pH optima as alkaline or acid phosphatases. For example, phosphatases are among the extracellular enzymes produced by Agaricus bisporus during growth on compost and must be important, therefore, in the nutrition of such litter degrading fungi.

But fungal phosphatases also serve as virulence factors in opportunistic fungal pathogens of humans because they do not respond to the control signals that regulate the host enzymes they mimic. However, the structural features that protect them from regulation by the host provide new opportunities for the development of inhibitors that specifically target the fungal enzymes without cross-reacting with host phosphatases. As several of the most common opportunistic fungal pathogens of humans are showing increasing resistance to conventional drugs, this is an area of therapeutics research with growing significance (Ariño et al., 2011; Chen et al., 2016).

 Sulfatases act on sulfate esters in the same way that phosphatases act on phosphate esters. They may be important in recovery of sulfate from the sulfated polysaccharides which are found in soils, and they also serve several functions in intermediary metabolism. Fungal sulfatases, like fungal phosphatases, have been associated with virulence in pathogenic fungi (Toesch et al., 2014; Chu et al., 2016).

Updated July, 2018