A Methylase is an enzyme that attaches a methyl group to a molecule, e.g. DNA methyltransferase which methylates cytosine residues or adenine residues in DNA.
A Methylase is an enzyme. An enzyme is e.g. DNA methyltransferase. This e.g. DNA methyltransferase methylates cytosine residues or adenine residues in DNA. This enzyme attaches a methyl group to a molecule.