AMT (aminomethyltransferase) is a mitochondrial matrix enzyme that catalyzes glycine degradation as a component of the glycine cleavage system [GO Annotations]. The protein functions as a transaminase that mediates glycine decarboxylation through the glycine cleavage complex, enabling the catabolic breakdown of glycine [GO Annotations]. This enzymatic activity is essential for amino acid metabolism and glycine homeostasis. Mutations in AMT result in glycine encephalopathy (also called non-ketotic hyperglycemia), a severe neurometabolic disorder characterized by excessive glycine accumulation in the central nervous system [Known Disease Associations]. Clinical manifestations include infantile-onset encephalopathy, intellectual disability, and seizures, reflecting the critical role of efficient glycine catabolism in neurological function. The disease severity correlates with the degree of enzymatic deficiency; complete loss of AMT activity causes early-infantile glycine encephalopathy with profound neurological consequences. Beyond primary glycine metabolism disorders, AMT dysfunction has been associated with broader genetic disorders and inflammatory conditions including Crohn's disease and inflammatory bowel disease, suggesting potential secondary metabolic contributions to these pathologies. AMT deficiency represents an important inborn error of amino acid metabolism requiring early diagnosis and therapeutic intervention to prevent irreversible neurological damage.