hydrolase activity, hydrolyzing O-glycosyl compounds endo-alpha-N-acetylgalactosaminidase activity https://github.com/geneontology/go-ontology/issues/25866 https://github.com/geneontology/go-ontology/issues/30193 Catalysis of the reactions : D-galactosyl-3-(N-acetyl-beta-D-galactosaminyl)-L-serine + H2O = D-galactosyl-3-N-acetyl-beta-D-galactosamine + L-serine and D-galactosyl-3-(N-acetyl-beta-D-galactosaminyl)-L-threonyl + H2O = D-galactosyl-3-N-acetyl-beta-D-galactosamine + L-threonyl. MetaCyc:3.2.1.97-RXN molecular_function endo-alpha-acetylgalactosaminidase activity GO:0033926 mucinaminylserine mucinaminidase activity D-galactosyl-3-(N-acetyl-alpha-D-galactosaminyl)-L-serine mucinaminohydrolase activity KEGG_REACTION:R04527 D-galactosyl-N-acetyl-alpha-D-galactosamine D-galactosyl-N-acetyl-galactosaminohydrolase activity RHEA:54540 RHEA:30983 EC:3.2.1.97 catalytic activity, acting on a glycoprotein