Amino acid
Amino acids are organic compounds containing amine (-NH) and carboxyl (-COOH) functional groups, along with a side chain (R group) specific to each amino acid. The key elements of an amino acid are carbon (C), hydrogen (H), oxygen (O), and nitrogen (N), although other elements are found in the side chains of certain amino acids. About 500 naturally occurring amino acids are known (though only 20 appear in the genetic code) and can be classified in many ways. They can be classified according to the core structural functional groups' locations as alpha- (α-), beta- (β-), gamma- (γ-) or delta- (δ-) amino acids; other categories relate to polarity, pH level, and side chain group type (aliphatic, acyclic, aromatic, containing hydroxyl or sulfur, etc.). In the form of proteins, amino acid residues form the second-largest component (water is the largest) of human muscles and other tissues. Beyond their role as residues in proteins, amino acids participate in a number of processes such as neurotransmitter transport and biosynthesis.
AOC3
Amine oxidases are a family of enzymes that catalyze the oxidation of various endogenous amines, including histamine or dopamine. VAP-1 constitutes the copper dependent class of amine oxidases, such as lysyl oxidase or lysine demethylase, and is one of the four known in humans. The other class is flavin dependent such as monoamine oxidase (MAO) A and B. VAP-1, in particular, catalyzes the oxidative conversion of primary amines (methylamine and aminoacetone) to aldehydes (formaldehyde and methylglyoxal) ammonium and hydrogen peroxide in the presence of copper and quinone cofactor.
VAP-1 is primarily localized on the cell surface on the adipocyte plasma membrane. However, circulating VAP-1 has been shown to be the main source of SSAO in human serum. Serum VAP-1 originates from many tissues. VAP-1 has adhesive properties, functional monoamine oxidase activity, and possibly plays a role in glucose handling, leukocyte trafficking, and migration during inflammation. This rise in metabolic products contributes to generating advanced glycation end-products and oxidative stress along with the monoamine detoxification in the organism.
Like monoamine oxidase (MAO), VAP-1 can deaminate short-chain primary amines, but SSAO enzymes, including VAP-1, can tolerate several selective flavin-dependent MAO-A and MAO-B inhibitors like clorgiline, pargyline, and deprenyl, but are still sensitive to semicarbazide and other hydrazines, hydroxylamine and propargylamine.
VAP-1 is found in the smooth muscle of blood vessels and various other tissues, and can mostly be found in two forms: tissue-bound and soluble isoforms. The tissue-bound SSAO is primarily located in the leukocytes, adipocytes, and the endothelium of highly vascularized tissues, including the kidney, liver, and gonads. Thus, this form participates in cellular differentiation, deposition of the ECM (extracellular matrix) in smooth muscle cells, lipid trafficking in adipocytes and control of muscular tone, by mechanisms that are not completely understood. The soluble form, which is commonly known as VAP-1, is a proinflammatory protein derived from shedding of the transmembrane protein. It is highly expressed on the endothelium of the lung and trachea, and absent from leukocytes and epithelial cells. It moderates leukocyte recruitment, is both an adhesion molecule and a primary amine oxidase, and plays a role in clinical disease.