Lysophosphatidic acid (LPA) and phosphatidic acid (PA) are two phospholipids involved in signal transduction and in lipid biosynthesis in cells. LPA acyltransferase (LPAAT), also known as 1-acyl sn-glycerol-3-phosphate acyltransferase (1-AGPAT) (EC 2.3.1.51), catalyzes the conversion of LPA to PA. Two human isoforms of LPAAT, designated as LPAAT-α (AGPAT1) and LPAAT-β (AGPAT2), have been extensively characterized. These two proteins contain extensive sequence similarities to microbial, plant and animal LPAAT sequences. LPAAT-α mRNA is uniformly expressed throughout most tissues with the highest level found in skeletal muscle; whereas LPAAT-β is differentially expressed, with the highest level found in heart and liver, and negligible level in brain and placenta. The LPAAT-α gene is located on chromosome 6p21.3, an area within the class III region of the major hiscompatibility complex (MHC) and the LPAAT-β gene is mapped to chromosome 9q34.3. Enhanced transcription of LPAAT-β is suggested for neoplasm of the female genital tract. Additionally, ectopic LPAAT expression in certain cytokine-responsive cell lines can effect amplification of cellular signaling processes, such as those leading to enhancement of synthesis of tumor necrosis factor-alpha and interleukin-6 from cells following stimulation with interleukin-1β; this suggests that the LPAAT genes represent candidates for affecting the development of certain cancers or inflammation-associated diseases.