Isolation, Ultrastructure, and Biochemical Characterization of Glycogen in Insect Flight Muscle

Abstract

Glycogen from flight muscle of the blowfly, Phormia regina, has been characterized ultrastructurally and biochemically . In situ, glycogen is in the form of rosettes, which vary in size with diameters of up to 0.1 µ . Sedimentation analysis of pure glycogen, isolated by mild buffer extraction, reveals a polydisperse molecular weight spectrum, with larger particles having molecular weights of 100 million . Treatment of native glycogen with alkali, under conditions usual for the extraction of the polysaccharide from tissues, results in a 5-to 10-fold reduction in molecular weight, as well as a chemical alteration of the molecule . Flight muscle phosphorylase has a lower affinity for native than for alkali-treated glycogen. The maximum velocity of the enzyme is also lower with native substrate . The apparent K. . for inorganic phosphate is higher with native glycogen as cosubstrate . These kinetic differences with native and partially degraded glycogen demonstrate the importance of using the natural substrate in studies of biochemical control mechanisms .When the blowfly initiates flight, an intense rate of glycogenolysis in the flight muscle is triggered (1) . The mechanisms of the control of glycogen utilization in the muscle is being studied . As part of this study, glycogen from blowfly flight muscle has been examined . This is of significance because of the observations that the physical and biological properties of the polysaccharide depend on the tissue of origin, the metabolic state of the tissue, and the method of extraction (2, 3) .Heretofore, glycogen from insects has not been characterized . In this paper, we report the isolation by mild buffer extraction of glycogen from flight muscle of the blowfly, Phormia regina, and describe its biophysical and biochemical properties. The polysaccharide has been found to be polydisperse, with a continuous spectrum of particle sizes up to 200 mµ, with the largest particles having molecular weights of 100 million . Marked differences in the kinetics of flight muscle phosphorylases with native and partially degraded glycogens, as substrates, indicate the importance of using native glycogen in studies of regulatory mechanisms . METHODS AND MATERIALS Raising of InsectsBlowflies, Phormia regina, were maintained in laboratory culture at 23'C and 12 hr of light per day . The larvae were reared on horsemeat, and the adult flies were fed powdered milk and sucrose . 7 days fol-

The Ultrastructure of the Indirect Flight Muscles of the Monarch Butterfly, Danaus plexippus (L.) with Implications for Fuel Utilization

“…2, 3, 4 and 7 ) which corresponds to the lower range of the size of beta glycogen particles (Fawcett 1966). This particulate component of the sarcoplasm has a distribution similar to the glycogen which Childress et al (1970) and Sacktor and Schimada (1972) digested with amylase in the blowfly. Light microscopic histochemical tests confirmed the presence of glycogen.…”

“…At 15 nm the electrondense granules found in the monarch butterfly flight muscle are in the lower size range of beta glycogen granules (Fawcett 1966). The distribution of the granules is similar to glycogen distribution in muscles which metabolize primarily glycogen: beta glycogen granules in vertebrate cardiac muscle (Fawcett 1966) and in Drosophila flight muscle (Shafiq 1963) and of alpha glycogen particles in blowfly flight muscle (Childress et al 1970, Sacktor andShimada 1972). Lui and Davies (1971) have discussed the possibility that the distribution of glycogen particles among the myofilaments may have metabolic significance.…”

Glycogen and Glucose Metabolism Are Essential for Early Embryonic Development of the Red Flour Beetle Tribolium castaneum

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Degenerative Changes in the Mitochondria of Flight Muscle From Aging Blowflies

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