Pyridoxamine is one form of vitamin B6. Chemically it is based on a pyridine ring structure, with hydroxyl, methyl, aminomethyl, and hydroxymethyl substituents. It differs from pyridoxine by the substituent at the 4-position. The hydroxyl at position 3 and aminomethyl group at position 4 of its ring endow pyridoxamine with a variety of chemical properties, including the scavenging of free radical species and carbonyl species formed in sugar and lipid degradation and chelation of metal ions that catalyze Amadori reactions. Pyridoxamine, also known as PM, belongs to the class of organic compounds known as pyridoxamine 5'-phosphates. These are heterocyclic aromatic compounds containing a pyridoxamine that carries a phosphate group at the 5'-position. Within humans, pyridoxamine participates in a number of enzymatic reactions. In particular, pyridoxamine can be converted into pyridoxal; which is mediated by the enzyme pyridoxine-5'-phosphate oxidase. In addition, pyridoxamine can be converted into pyridoxamine 5'-phosphate; which is catalyzed by the enzyme pyridoxal kinase. Pyridoxamine also inhibits the formation of advanced lipoxidation endproducts during lipid peroxidation reactions by reaction with dicarbonyl intermediates. In humans, pyridoxamine is involved in vitamin B6 metabolism. Outside of the human body, pyridoxamine has been detected, but not quantified in several different foods, such as nutmegs, sparkleberries, fennels, turmerics, and swiss chards. Pyridoxamine inhibits the Maillard reaction and can block the formation of advanced glycation endproducts, which are associated with medical complications of diabetes. Pyridoxamine is hypothesized to trap intermediates in the formation of Amadori products released from glycated proteins, possibly preventing the breakdown of glycated proteins by disrupting the catalysis of this process through disruptive interactions with the metal ions crucial to the redox reaction. One research study found that pyridoxamine specifically reacts with the carbonyl group in Amadori products, but inhibition of post-Amadori reactions (that can lead to advanced glycation endproducts) is due in much greater part to the metal chelation effects of pyridoxamine.