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Acid phosphatases (APase) are a family of enzymes that non-specifically catalyze the hydrolysis of monoesters and anhydrides of phosphoric acid to produce inorganic phosphate at an optimum pH of 4 to 7 by the following reaction:
APase
R-PO4 + H2O ® R-OH + HOPO3
2+
Their function in the production, transport, and recycling of phosphate is critical for the metabolic and energy transduction processes of the cell. As a group, APases
may be as important as kinases in regulatory processes.
Plant APases have been localized in the cytosol,vacuoles, and cell walls. One key role is phosphate acquisition to mobilize organic phosphates in the soil.2 Phosphate starvation also induces APase generation.Potato tuber APase is a monomeric glycoprotein. The carbohydrate component makes up 16.6% of the molecular mass.3
Molecular mass:3 69 kDa
Carbohydrate residues (%):3
Mannose 5.0
Glucosamine 3.6
Rhamnose 3.4
Glucose 2.5
Galactose 1.5
pH Optimum:3 5.0–5.3
pH Range:4 4–7
Temperature optimum: 37 °C
Substrates:3,5
a-glyceryophosphate ATP
fructose-6-phosphate fructose-6-phosphate
inorganic pyrophosphate glucose-6-phosphate
p-nitrophenyl phosphate
KM (mM):3
p-nitrophenyl phosphate 1.25
inorganic pyrophosphate 40.0
Activators:6
Cu2+, Mg2+, Mn2+, Zn2+, Hg2+ (below 0.4 mM)
Inhibitors:3,6
Al3+, Hg2+ (above 0.4 mM), MoO4
2–, Zn2+, urea
12