Dioscorins from different Dioscorea species all exhibit both carbonic anhydrase and trypsin inhibitor activities

Dioscorins, the storage proteins of yam tubers, from six cultivars of three Dioscorea species including D. batatas, D. alata, and D. pseudojaponica were detected in crude extracts of yam tubers but not leaves by immuno stainings on PVDF membrane with a polyclonal antibody which was raised against 28 kDa dioscorin from Dioscorea batatas Decne. It was demonstrated that the dioscorins from the above-mentioned yam species exhibited both carbonic anhydrase (CA) and trypsin inhibitor activities by activity stainings on 15% SDS-PAGE gels. Dioscorins were identified as glycoproteins by ConA-peroxidase activity staining. Dioscorins from D. batatas Decne contained no zinc atoms detectable by atomic absorption spectrophotometry. Neither 5 mM acetazolamide nor 2,6-pyridinedicarboxylic acid inhibited the CA activity of dioscorins.