What are the sources of methionine? The two most well-known and commonly used sources today are DL methionine and DL hydroxy methionine. What's the difference between them? These molecules are in reality very similar except for one difference. DL methionine features an amino group on carbon in R2. DL hydroxy methionine is produced by replacing the NH2 group with a hydroxy OH group. By DNL. The chemical synthesis process produces the 2D in L forms and identical quantities, 50% form D and 50% form L. As you can see, it is the same molecule with a different configuration. In other words, one is the mirror of the other. Like two hands opposite each other that can never be placed one on top of the other. DL methionine and DL hydroxy methionine are both transformed in the body to be assimilated in used in different metabolic cycles. How does this transformation take place? The hydroxy and amino groups are replaced in the body by a ketone group. The asymmetry disappears and an intermediate KMB is produced that is then transformed into L methionine by replacing the ketone group with an amino group. These two molecules are two equivalent sources of methionine as similar by animals.