SHMT1 (serine hydroxymethyltransferase 1) is a pyridoxal phosphate-dependent enzyme that catalyzes the reversible conversion of serine and tetrahydrofolate to glycine and 5,10-methylene tetrahydrofolate, serving as a critical component of folate metabolism and one-carbon biosynthesis 1. The enzyme provides one-carbon units essential for DNA synthesis, methylation, and biosynthesis of methionine, purines, and pyrimidines 2. SHMT1 functions through multiple mechanisms: it acts as a metabolic enzyme facilitating serine-glycine interconversion, serves as a nuclear scaffold protein anchoring thymidylate synthesis complexes to DNA replication sites, and possesses RNA-binding capability that regulates cellular metabolism 1. The enzyme exhibits riboregulation, where RNA binding acts as an allosteric switch that selectively alters enzymatic reactivity toward serine 1. Disease relevance includes associations with cancer susceptibility, particularly non-Hodgkin lymphoma risk through the C1420T polymorphism 3, and potential protective effects against colorectal cancer in certain populations 2. SHMT1 variants are also associated with multiple sclerosis susceptibility 4 and have been identified as potential therapeutic targets for neurodegenerative diseases 5. Clinical significance extends to muscle hypertrophy, where SHMT1 genetic variations correlate with appendicular lean mass 6, highlighting its broader role in cellular growth and metabolism.