Enables glycerol-3-phosphate O-acyltransferase activity. Involved in triglyceride biosynthetic process. Acts upstream of or within several processes, including acylglycerol metabolic process; glandular epithelial cell maturation; and lactation. Located in endoplasmic reticulum. Is expressed in several structures, including adipose tissue; brain; genitourinary system; liver; and mammary gland. Orthologous to human GPAT4 (glycerol-3-phosphate acyltransferase 4). [provided by Alliance of Genome Resources, Apr 2022]