SHMT1

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. 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. 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. 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. 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. 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..

Function from UniProtKB (P34896), read 2026-09-23. CC BY 4.0.