title: 5-Methyldeoxycytidine monophosphate deaminase and 5-methylcytidyl-DNA deaminase activities are present in human mature sperm cells.
abstract: Human mature sperm cells have a high nuclease and 5-methyldeoxycytidine monophosphate (5-mdCMP) deaminase activity. The deaminase converts the nuclease degradation product 5-mdCMP into dTMP which is further cleaved into thymine and the abasic sugar-phosphate. Both 5-methylcytidine 5' and 3' monophosphates are good substrates for the deaminase. 5-methylcytidine is not a good deaminase substrate and 5-methylcytosine (5mC) is not a substrate. A purified fraction of the deaminase free of nucleases deaminates 5mC present in intact methylated double-stranded DNA. 5-mdCMP deaminase co-purifies on SDS-PAGE with dCMP deaminase and has an apparent molecular weight of 25 kDa. The enzyme requires no divalent cations and has a Km of 1.4 x 10(-7) M for 5-mdCMP and a Vmax of 7 x 10(-11) mol/h/microg protein. The possible biological implications of the deaminase's activities in the present system are discussed.
authors.affiliation: Friedrich Miescher Institute, Maulbeerstrasse 66, Basel, Switzerland. jost@fmi.ch
authors.forename: Jean Pierre
authors.initials: JP
authors.lastname: Jost
authors.forename: Stéphane
authors.initials: S
authors.lastname: Thiry
authors.forename: Michel
authors.initials: M
authors.lastname: Siegmann
mesh_terms: D000619:Aminohydrolases / Q000737:chemistry / Q000378:metabolism*; D003562:Cytidine / Q000031:analogs & derivatives* / Q000737:chemistry; D004247:DNA / Q000378:metabolism; D003843:Deoxycytidine Monophosphate / Q000031:analogs & derivatives* / Q000737:chemistry; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D006801:Humans; D008297:Male; D008970:Molecular Weight; D009841:Oligonucleotides / Q000737:chemistry; D013094:Spermatozoa / Q000737:chemistry / Q000201:enzymology*; D013379:Substrate Specificity; D013941:Thymine / Q000032:analysis / Q000096:biosynthesis; D014498:Uracil / Q000032:analysis / Q000096:biosynthesis
chemical_list: D009841:Oligonucleotides; D003843:Deoxycytidine Monophosphate; C007261:deoxy-5-methylcytidylic acid; D014498:Uracil; D003562:Cytidine; D004247:DNA; C457060:5-methyldeoxycytidine monophosphate deaminase; D000619:Aminohydrolases; D013941:Thymine; C016568:5-methylcytidine