Catalyzes the interconversion of serine to glycine accompanied with the production of 5,10-methylenetetrahydrofolate, a source of one-carbon units used by thymidylate synthase to convert dUMP to dTMP for DNA synthesis (PubMed:11071283, PubMed:19591883, PubMed:24914963). Binds to its own mRNA and to the mRNA of bifunctional dihydrofolate reductase-thymidylate synthase (DHFR-TS) in vitro; the physiological relevance of this interaction is not clear (PubMed:19591883). (6R)-5,10-methylene-5,6,7,8-tetrahydrofolate + glycine + H2O = (6S)-5,6,7,8-tetrahydrofolate + L-serine Redox regulation; active in reducing conditions, inactive in oxidizing conditions. The reduction of the cysteine pairs allows the access binding of the tetrahydrofolate substrate to its binding site. This mechanism appears to be unique to Plasmodium species. kcat is 3.71 sec(-1) with L-serine and tetrahydrofolate as substrates (at 37 degrees Celsius) (PubMed:19591883). kcat is 9.4 min(-1) with L-serine and tetrahydrofolate as substrates (at 37 degrees Celsius) (PubMed:19591883). One-carbon metabolism; tetrahydrofolate interconversion. Homodimer. Predominantly localizes to the cytoplasm in early trophozoites and postmitotic schizonts. Transiently localizes to the mitochondrion and the apicoplast in late trophozoites and in mitotic schizonts. Partially localizes to the nucleus, especially in late trophozoites and in mitotic schizonts. Expressed during the parasite erythrocyte stages, namely in trophozoites and schizonts. Belongs to the SHMT family.