Catalyzes the condensation of L-serine with palmitoyl-CoA (hexadecanoyl-CoA) to produce 3-oxosphinganine (PubMed:11279212, PubMed:17557831, PubMed:17559874, PubMed:19376777). Exhibits a broad substrate specificity concerning the chain length and the degree of unsaturation of acyl-CoA (PubMed:11279212, PubMed:19376777). H(+) + hexadecanoyl-CoA + L-serine = 3-oxosphinganine + CO2 + CoA Not inhibited by relatively high concentrations of palmitoyl-CoA (PubMed:11279212). Inhibited by both D-cycloserine (DCS) and L-cycloserine (LCS), which inactivate SPT by transamination to form a free pyridoxamine 5'-phosphate (PMP) and beta-aminooxyacetaldehyde that remain bound at the active site (PubMed:20445930). Inhibition is reversed by incubation with excess pyridoxal phosphate (PubMed:20445930). Inhibited by the fungal natural product myriocin, which acts as a competitive inhibitor for both L-serine and palmitoyl-CoA substrates (PubMed:23957439). kcat is 140 min(-1) with palmitoyl-CoA as substrate (PubMed:11279212). kcat is 2.3 sec(-1) with palmitoyl-CoA as substrate (PubMed:17557831). kcat is 1.150 sec(-1) with palmitoyl-CoA as substrate (PubMed:19376777). kcat is 0.045 sec(-1) with decanoyl-CoA as substrate (PubMed:19376777). kcat is 0.262 sec(-1) with lauroyl-CoA as substrate (PubMed:19376777). kcat is 0.601 sec(-1) with myristoyl-CoA as substrate (PubMed:19376777). kcat is 0.898 sec(-1) with stearoyl-CoA as substrate (PubMed:19376777). kcat is 0.327 sec(-1) with arachidoyl-CoA as substrate (PubMed:19376777). Optimum pH is 7.5 to 8.0. Lipid metabolism; sphingolipid metabolism. Homodimer. Distributed throughout the cytoplasm. Belongs to the class-II pyridoxal-phosphate-dependent aminotransferase family.