protein-L-isoaspartate (D-aspartate) O-methyltransferase activity
protein-l-isoaspartate (d-aspartate) o-methyltransferase activity
Catalysis of the reaction: S-adenosyl-L-methionine + protein L-beta-aspartate = S-adenosyl-L-homocysteine + protein L-beta-aspartate methyl ester.