Secreted effector that suppresses host plant glucan elicitor-mediated defense responses (PubMed:18624645). Targets host endoglucanases and inhibits the endoglucanase-mediated release of elicitor-active glucan oligosaccharides from P.infestans cell walls (PubMed:18624645). Forms an apoplastic complex with host endoglucanases in tomato leaves during P.infestans infection. Expressed during infection and the expression levels increase with disease progression. Belongs to the peptidase S1 family. None of the predicted glucanase inhibitor proteins (GIPS) has an intact catalytic triad, therefore, GIPs are proteolytically inactive.