SPTLC1 and neurodegenerative disease: Human SPT is a membrane-bound large protein complex containing SPTLC1/SPTLC2 heterodimer as the core subunits, and it is known that mutations of the SPTLC1/SPTLC2 genes increase the formation of deoxy-type of LCBs derived from l-Ala and Gly to cause some neurodegenerative diseases.