Several genetic variants have been identified, the main ones in the cow being labelled A and B. Because of its abundance and ease of purification, it has been subjected to a wide range of biophysical studies.
Identificáronse varias variantes xenéticas, as principais no leite de vaca son as denominadas A e B. Debido á súa abundancia e facilidade de purificación, fixéronse con ela numerosos estudos biofísicos.