Deoxyribonucleic acid methylase activity in pea seedlings.

Deoxyribonucleic acid methylase activity has been detected in a preparation of disrupted nuclei prepared from pea seedlings. S-Adenosyl-L-methionine acted as a donor of methyl groups, and the product of the reaction was identified as 5-methylcytosine. The reaction had a sharp temperature optimum at about 30 degrees C and was unusual in that the DNA methylase was able to methylate DNA in the crude extract.