The function of Ensembl gene identifier ENSG00000176974 (SHMT1, serine hydroxymethyltransferase 1) is as follows. Pyridoxal phosphate (PLP)-dependent enzyme that catalyzes the reversible conversion of serine and tetrahydrofolate (THF) to glycine and 5,10-methylene THF, serving as a critical component of the folate cycle and facilitating one-carbon biosynthetic reactions essential for methionine, purine, and pyrimidine synthesis (PubMed:24698160, PubMed:30035852, PubMed:38996576). While its central activity involves serine cleavage, the detailed catalytic mechanisms remain under study, including both retro-aldol cleavage of the PLP-serine C(alpha)-C(beta) bond followed by formaldehyde condensation with THF, and alternative nucleophilic displacement mechanisms of the C(alpha) atom of PLP-serine aldimine involving THF's N5 atom (By similarity). Also catalyzes the cleavage of various 3-hydroxy amino acids, such as L-allo-threonine, L- threonine and 3-phenylserine, forming glycine and the corresponding aldehyde through a retro-aldol process; additionally, it catalyzes the formation of 5-formyltetrahydrofolate from 5,10- methenyltetrahydrofolate (PubMed:38615009). Also functions as a hydroxytrimethyllysine aldolase (HTMLA) catalyzing the second step of the carnitine biosynthesis pathway and exhibits substrate preference with the erythro (S,S) configuration, and more efficiency with L-allo- threonine (PubMed:38615009). In the nucleus, first functions as a lamin-binding scaffold protein that is essential for assembling the de novo thymidylate synthesis complex by co-localizing DHFR and TYMS with the nuclear lamina and anchoring the complex to DNA replication sites (PubMed:22235121). Subsequently, provides one-carbon substrates, specifically (6R)-5,10-methylene-5,6,7,8-tetrahydrofolate, in situ for de novo dTMP synthesis to sustain DNA replication and repair during cell proliferation (PubMed:30035852). Importantly, possesses RNA- binding capability, forming complexes that selectively regulate SHMT2 mRNA translation and dynamically modulate cytosolic and mitochondrial serine and glycine concentrations, thus influencing cellular metabolic status (PubMed:38996576). {ECO:0000250|UniProtKB:P07511, ECO:0000269|PubMed:22235121, ECO:0000269|PubMed:24698160, ECO:0000269|PubMed:30035852, ECO:0000269|PubMed:38615009, ECO:0000269|PubMed:38996576}.