Endogenous lectin as a possible regulator of the hydrolysis of physiological substrates by soybean seed acid phosphatase

The effects of two lectins concanavalin A (conA) and soybean agglutinin, on soybean seed acid phosphatase activity were investigated using p-nitrophen ylphosphate (pNPP), pyrophosphate (PPi) and phosphoenolpyruvate (PEP) as su bstrates. Of the four acid phosphatase isoforms (AP1, AP2, AP3A and AP3B) p urified from soybean seeds, only API was activated 40 and 60% by conA and s oybean agglutinin, respectively. Both lectins affected some of the kinetic parameters of AP1. The activation by lectins was not affected by 1 mM Ca2or Mn2+ but glucose and methylmannopyranoside (100 mM) prevented activation by conA. Under the same conditions, galactose had no effect. These results suggest that plant acid phosphatases may be regulated by lectins, the effe cts vary according to the substrate used. (C) 2001 Elsevier Science Ltd. Al l rights reserved.