Thyroid Membrane Nad-Glycohydrolase and Adp•Ribosyl-Transferase, Possibly Relevant to TSH Action
Cholera toxin stimulates the adenylate cyclase complex by mono-ADPribosylating the guanine regulatory component (N-protein) . Although cholera toxin and thyrotropin (TSH) have structural and functional similarities , clear-cut discrepancies exist in their mode of action. Thus, neither TSH nor its α-subunit have any intrinsic ADPribosyltransferase or NAD-glycohydrolase (NADase) activity. However, in bovine thyroid membranes both activities are present , the ADPribosylation being stimulated by TSH, and with prolonged incubation the hormone itself is ADPribosylated . These enzymic activities are probably related and so are here designated as enzyme system E1. Possibly other enzyme activities are implicated in E1.
KeywordsSialic Acid Cholera Toxin Sulphanilic Acid Thyroid Adenoma Sialic Acid Content
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