{"doi":"10.1073/pnas.69.10.2910","title":"Inactivator of the Third Component of Complement as an Inhibitor in the Properdin Pathway","abstract":"<jats:p>Evidence has been obtained that a single protein, known to modulate classical complement activation, also acts as an inhibitor in the properdin or alternate complement pathway. A highly purified inactivator of the third component of complement (C3) from human serum inhibited the proteolysis of Factor B in the properdin system (glycine-rich β-glycoprotein) by glycine-rich β-glycoproteinase. The inhibition was by the enzymatic destruction of glycine-rich β-glycoproteinase activity. The major fragment of C3, C3b, which is the only known substrate of the C3 inactivator, blocked the destruction of glycine-rich β-glycoproteinase by the C3 inactivator. Thus, in its inhibition of the porperdin pathway, the C3 inactivator destroys both the active form of glycine-rich β-glycoproteinase and a protein involved in the conversion of the zymogen form of this enzyme (proglycine-rich β-glycoproteinase) to its active form. The increased susceptibility to infections in a patient homozygous for deficiency of the C3 inactivator demonstrates the biologic significance of this protein.</jats:p>","journal":"Proceedings of the National Academy of Sciences","year":1972,"id":616289,"datarank":0.6995158641168101,"base_score":4.663439094112067,"endowment":4.663439094112067,"self_citation_contribution":0.6995158641168101,"citation_network_contribution":0.0,"self_endowment_contribution":0.6995158641168101,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":105,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":null,"is_data_producer":false,"deposit_databanks":null,"is_oa":false,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":null,"fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":1588818,"name":"Fred S. 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The major fragment of C3, C3b, which is the only known substrate of the C3 inactivator, blocked the destruction of glycine-rich β-glycoproteinase by the C3 inactivator. Thus, in its inhibition of the porperdin pathway, the C3 inactivator destroys both the active form of glycine-rich β-glycoproteinase and a protein involved in the conversion of the zymogen form of this enzyme (proglycine-rich β-glycoproteinase) to its active form. 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