The functional enzyme is a heterodimer of SPT1 (LCB1) with either SPT2 (LCB2) or SPT3 (LCB2B); the small subunits of SPT (ssSPTa or ssSPTb) bind to the heterodimer to enhance enzymatic activity. The complexes of SPT1/SPT2/ssSPTa and SPT1/SPT2/ssSPTb were most active with palmitoylCoA as substrate, with the latter complex also showing some activity with stearoylCoA [1]. Complexes involving SPT3 appeared more broad in substrate selectivity, with incorporation of myristoylCoA prominent for SPT1/SPT3/ssSPTa complexes, while SP1/SPT3/ssSPTb complexes had similar activity with C16, C18 and C20 acylCoAs [1].

1. Han G, Gupta SD, Gable K, Niranjanakumari S, Moitra P, Eichler F, Brown Jr RH, Harmon JM, Dunn TM. (2009) Identification of small subunits of mammalian serine palmitoyltransferase that confer distinct acyl-CoA substrate specificities. Proc Natl Acad Sci USA, 106 (20): 8186-91. [PMID:19416851]

2. Hoch DG, Abegg D, Hannich JT, Pechalrieu D, Shuster A, Dwyer BG, Wang C, Zhang X, You Q, Riezman H et al.. (2020) Combined Omics Approach Identifies Gambogic Acid and Related Xanthones as Covalent Inhibitors of the Serine Palmitoyltransferase Complex. Cell Chem Biol, 27 (5): 586-597.e12. [PMID:32330443]

3. Miyake Y, Kozutsumi Y, Nakamura S, Fujita T, Kawasaki T. (1995) Serine palmitoyltransferase is the primary target of a sphingosine-like immunosuppressant, ISP-1/myriocin. Biochem Biophys Res Commun, 211 (2): 396-403. [PMID:7794249]