Human Metabolome Database (HMDB): Methylamine occurs endogenously from amine catabolism and its tissue levels increase in some pathological conditions, including diabetes. Interestingly, methylamine and ammonia levels are reciprocally controlled by a semicarbazide-sensitive amine oxidase activity that deaminates methylamine to formaldehyde with the production of ammonia and hydrogen peroxide. Methylamine also targets the voltage-operated neuronal potassium channels, probably inducing release of neurotransmitter(s). Semicarbazide-sensitive amine oxidase (SSAO) catalyzes the deamination of primary amines. Such deamination has been shown capable of regulating glucose transport in adipose cells. It has been independently discovered that the primary structure of vascular adhesion protein-1 (VAP-1) is identical to SSAO. Increased serum SSAO activities have been found in patients with diabetic mellitus, vascular disorders and Alzheimer's disease. The SSAO-catalyzed deamination of endogenous substrates like methylamine led to production of toxic formaldehyde. Chronic elevated methylamine increases the excretion of malondialdehyde and microalbuminuria. Amine oxidase substrates such as methylamine have been shown to stimulate glucose uptake by increasing the recruitment of the glucose transporter GLUT4 from vesicles within the cell to the cell surface. Inhibition of this effect by the presence of semicarbazide and catalase led to the suggestion that the process is mediated by the H (2) O (2) produced in the oxidation of these amines. (PMID: 16049393, 12686132, 17406961).