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5‐Methyldeoxycytidine monophosphate deaminase and 5‐methylcytidyl‐DNA deaminase activities are present in human mature sperm cells
Author(s) -
Jost Jean-Pierre,
Thiry Stéphane,
Siegmann Michel
Publication year - 2002
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/s0014-5793(02)02737-0
Subject(s) - amp deaminase , biochemistry , chemistry , thymine , nuclease , cytidine deaminase , enzyme , deamination , dna , microbiology and biotechnology , biology , adenosine deaminase
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 K m of 1.4×10 −7 M for 5‐mdCMP and a V max of 7×10 −11 mol/h/μg protein. The possible biological implications of the deaminase's activities in the present system are discussed.