A1M

A1M, short for alpha-1-microglobulin, is a small secreted glycoprotein of the lipocalin family that circulates in human blood plasma and is present in various body fluids, including urine. It is encoded by the A1M gene and is produced predominantly by the liver, with release into the circulation and subsequent distribution to tissues. In the kidney, A1M is filtered from the blood and can be reabsorbed by proximal tubule cells.

Biochemically, A1M is a single-chain protein characterized by the structural features of lipocalins. It exists mainly as a monomer in plasma and undergoes post-translational modifications such as N-linked glycosylation. A1M has binding capacity for small hydrophobic ligands and for heme and other byproducts of oxidative stress, contributing to its role in detoxification and protection against cellular damage.

Functionally, A1M acts as an antioxidant and cytoprotective factor. It participates in scavenging free radicals and lipid peroxidation products and binding free heme, thereby reducing oxidative injury in tissues. Its presence in plasma and urine supports a protective role during inflammatory or oxidative conditions, ischemia-reperfusion injury, and other stress states. In the kidney, A1M helps mitigate tubular damage by maintaining redox balance and clearing harmful byproducts.

Clinically, A1M is studied as a biomarker of kidney tubular injury, with elevated urinary A1M indicating proximal tubule dysfunction in various renal disorders. Research also explores therapeutic applications of A1M or A1M-based derivatives to limit tissue injury from oxidative stress and hemorrhagic or inflammatory conditions. As a gene product, variations in A1M expression or function are of ongoing scientific interest in nephrology and related fields.