C-type lysozyme (1, 4-beta-N-acetylmuramidase, LYZ) and alpha-lactalbumin (lactose synthase B protein, LA). They have a close evolutionary relationship and similar tertiary structure, however, functionally they are quite different. Lysozymes have primarily bacteriolytic function; hydrolysis of peptidoglycan of prokaryotic cell walls and transglycosylation. LA is a calcium-binding metalloprotein that is expressed exclusively in the mammary gland during lactation. LA is the regulatory subunit of the enzyme lactose synthase. The association of LA with the catalytic component of lactose synthase, galactosyltransferase, alters the acceptor substrate specificity of this glycosyltransferase, facilitating biosynthesis of lactose.