This invention relates to an isolated nucleic acid fragment encoding a serine palmitoyltransferase Lcb1 subunit. The invention also relates to the construction of a chimeric gene encoding all or a portion of the serine palmitoyltransferase Lcb1 subunit, in sense or antisense orientation, wherein expression of the chimeric gene results in production of altered levels of the serine palmitoyltransferase Lcb1 subunit in a transformed host cell.