Phosphatidylglycerophosphatase (EC 184.108.40.206) activity was characterized in mitochondrial extracts from Saccharomyces cerevisiae. The enzyme has a pH optimum of 5.5. Maximum activity occurs in the presence of Triton X-100 (5 mM) and cobalt or magnesium ions (5 mM). The apparent Km for PGP is 14.6 microM. The temperature optimum is between 50 degrees C and 60 degrees C. The enzyme is labile above 50 degrees C. The presence of inositol in growth media results in a slight but reproducible increase in PGPase activity in mitochondrial extracts from glucose-grown cells but not glycerol-grown cells. The inositol effect is not seen in crude cell extracts. Carbon source does not affect PGPase activity in mitochondrial extracts or in crude cell extracts.