PURPOSE: To verify the expression of the mouse homolog of glucosamine-6-phosphate deaminase (GNPDA) in the testis and reproductive organs. MATERIALS AND METHODS: Expression of GNPDA was examined using a polyclonal antibody raised against a synthetic oliogopeptide of the N-terminus of the protein. RESULTS: In Western blots, an immunoreactive band of Mr 35 kDa was detected in the testis, ovary, and uterus extracts. Expression of GNPDA was greater in the adult than in the immature testis. With immunostaining, a positive signal was found in the cytoplasm of interstitial, Sertoli, and germ cells of adult testis. In the ovary, positive staining was found in the interstitial and luteal cells. Conclusion: The expression of GNPDA in many reproductive tissues suggests that the enzyme plays a housekeeping role in cell physiology and in the differentiation of the seminiferous tubules.