OBJECTIVE	The methyltransferase genes were arsenic ( + III oxidation state ) methyltransferase ( AS3MT ) , DNA-methyltransferase 1a and 3b ( DNMT1a and DNMT3b , respectively ) , phosphatidylethanolamine N-methyltransferase ( PEMT ) , and betaine-homocysteine methyltransferase ( BHMT ) .\