Investigations on the Mitochondria of the House Fly, Musca Domestica L. I . Adeno Sinetripho Sphata Ses by Bertram Sacktor

In the course of studying synthetic processes associated with mitochondria of insects, it was found that the preparations contain enzymes which presumably could interfere with synthesis by breaking down ATP. 1 A systematic investigation of the dephosphorylating mechanisms was therefore undertaken in order to ascertain the significance of such opposing reactions. With the possible exclusion of the enzymes found in mammalian mnscles which split phosphate from ATP, the nature of this activity in tissues remains partially obscure. Dephosphorylation of ATP by liver mitochondria has been reported by Kielley and Kielley (1951) and Novikoff et al. (1952). Swanson (1951) characterized "soluble" ATPase obtained from the supernatant of liver fractions. A "soluble" ATPase from muscle has also been described by Kielley and Meyerhof (1948). Meyerhof and Ohlmeyer (1952) achieved a 50-fold purification of yeast ATPase. Pyro-pase activity has also been found in yeast (Bailey and Webb, 1944), in liver (Swanson, 1952), and in other tissues. These few data are admittedly insufficient for a satisfactory resolution of the mechanism of dephosphorylation in mammalian tissues, and in insects practically nothing is known of adenine nucleotide breakdown; in fact, the mere presence of ATP in insects has only recently been affirmed by Albaum and Kletzkin (1948) and Calaby (1951), while the dephosphorylation of ATP has been but briefly noted. Gilmour (1948) found a soluble enzyme derived from grasshopper myosin extracts which splits both labile phosphates from the ATP molecule. He also noted that grasshopper muscle contains an enzyme which hydrolyzes inorganic Pyro-P. An apyrase was observed in cockroach muscle homogenates by Barton and Tahmisian (1948) and Chin (1951). The latter claimed that his preparation was specific for ATP in so far as no phosphorns was split from H-P or Gly-P.