Lipoprotein(a) and L carnitine TMAO: how gut microbiota contributes to heart failure Translational Research L carnitine is primarily synthesized in the liver from the amino acids lysine and methionine through a series of four enzymatic reactions, with the liver and kidneys converting the precursor butyrobetaine into active Pure Encapsulations Acetyl l Carnitine 60 Caps Pure Integrative Pharmacy ACETYL L CARNITINE 250 MG 60 CAPS PURE ENCAPSULATION