L-N6-(1-iminoethyl)lysine 5-tetrazole amide (SC-51 or L-NIL-TA) is rapidly converted in vivo to the active metabolite L-N6-(1-iminoethyl)lysine (L-NIL). L-NIL is a relatively selective inhibitor of nitric-oxide synthase type 2 (NOS2). Unlike L-NIL, L-NIL-TA has minimal inhibitory activity in vitro on human NOS2. However, it is rapidly converted in vivo to L-NIL and produces dose-dependent inhibition of iNOS in acute and chronic models of inflammation in the rodent with efficacy comparable to L-NIL. L-NIL-TA produces marked inhibition of exhaled breath NO in normal and asthmatic subjects without producing the side effects observed following the systemic administration of non-selective NOS inhibitors, and thus provides support for the potential use of iNOS inhibitors to treat a range of inflammatory clinical disorders.

S-Adenosyl-L-homocysteine (SAH), a potent methyltransferase inhibitor and a substrate of the s-adenosylhomocysteine hydrolase, is an amino acid derivative and an intermediator or modulator of several metabolic pathways, including the activated methyl cycle and cysteine biosynthesis. It was shown, that the plasma SAH might be a novel biomarker for the early clinical identification of cardiovascular disease. In addition, the elevated SAH in Alzheimer's brain was related to markers of disease progression and cognitive impairment.