The Enzymatic Architecture of the Unfertilized Oyster Egg

Abstract

In a previous paper (Cleland, 1950b) some aspects of the intermediary metabolism of the unfertilized oyster egg were detailed. A study of the enzymatic architecture of the cell seemed desirable since this knowledge is necessary for a clear formulation of the problems of cell division and differentiation in relation to metabolism (Cleland, 1950a) and would relate the metabolism of the egg to a previous study of cell architecture (Cleland, 1947). Such a study was made in the 1949 and 1950 seasons and forms the basis of this paper.In Tecent years cell respiration has been shown to be intimately connected ^rith cell granules. While mitochondria were very early linked with cell metabolism (cf. Cowdry, 1918) a specific connection with respiration was first suggested by Kingsbury (1912) and Mayer et al. (1914). Although Warburg (1914) demonstrated that much of the oxidative activity of sea urchin egg brei was associated with the granular components, the relevance of the finding to the mitochondrial problem was not appreciated and this type of study lapsed. The mitochondria respiration relation was supported by Joyet Lavergne (1927-38) but none of this work can be considered conclusive.Studies of centrifugally-broken Arbacia eggs provided a number of suggestive facts. The experiments of Shapiro (1935) indicated that the heavy halves, which contain the pigment granules and about three-quarters of the yolk granules, havo a higher endogenous respiration than the light halves, and Ballentine (1940) from his study of the distribution of reducing systems considered that they were associated with the granules. These studies were not extended to quarter eggs in which granule fractionation is more satisfactory. Hutchens et al. (1942) made a study of the distribution of cytochrome oxidase in various fractions separated from sea urchin egg homogenates. They were led to conclude that a considerable fraction was present in the ground cytoplasm where it was also most active in terms of total N. This finding is diflScult to reconcile with that of Navez and Harvey (1935) and with more recent reports.Mitochondria were first separated from cells, and analysed, by Bensley and Hoerr (1934) but seven years elapsed before their respiratory characteristics were examined by Lazarow (1943), Lazarow and Barron (1941). Chantrenne (1944) showed that cytochrome oxidase and succinoxidase are present in the granules separated from yeast and other cells. Schneider (]946a) and Hogeboom et al. (1946) demonstrated the presence of succinoxidase and cytochrome oxidase on the mitochondrial fraction. The presence of the tricarboxylic acid cycle and fatty acid oxidase in mitochondria was demonstrated by Kennedy and Lehninger (1949).Most of the recent work has been done on mitochondria from mammalian liver and little attention has been paid to the general validity of the distribution. However, Recknagel (1950) has shown that cytochrome oxidase is associated with the mitochondrial fraction of the frog's egg, the large yolk granules having little activity, ...

Respiratory granules of heart muscle

“…these particles possessed no succinic oxidase activity. The enzyme distribution in the microsome fraction of the oyster egg is also different from the distribution in the mitochondria or yolk granules (Cleland, 1951). Although the particles of the Keilin & Hartree preparation are similar in size to the microsomes, their high respiratory activity distinguishes them sharply from liver microsomes.…”

“…The phosphate-saline medium, which was used in a previous study (Slater, 1950 a) and is similar to that used by Ochoa (1944), is in effect considerably hypotonic because HPO42-, the major anion of the phosphate buffer at pH 7 1-7-3 enters the sarcosomes and is not, therefore, osmotically active (Cleland, 1952). The saline and saline-Versene media are approximately isotonic with blood.…”

“…First, isolated sarcosomes are able rapidly to react with both oxidized and reduced cytochrome c, which being a protein would not be expected to penetrate a membrane. Secondly, succinate which is rapidly oxidized by heart-muscle sarcosomes has been show-n not to penetrate the membrane (Cleland, 1952). These observations are easily explained if it is assumed that cytochrome c and succinate react with components which are situated on the surface of the sarcosome.…”

Mitochrondria from embryonic tissues of the chick. 2. Metabolic activities

“…Spratt (1952) has show-n a number of dehydrogenases, including those for pyruvate, 2-oxoglutarate, succinate and malate, to be present in chick blastoderms. It may also be mentioned that oxidation of intermediates of the tricarboxylic acid cycle has been observed with homogenates of eggs of the oyster O8trea commerciaw18 (Cleland, 1951) and of eggs of the sea urchin Echinu.s eaculentu8 (Cleland & Rothschild, 1952). In early stages of cleavage of the eggs of the sea urchin Arbacia, however, the tricarboxylic acid cycle seems to be less important than the pentose phosphate pathway (Krahl, 1956).…”

The Concentrations of Some Enzymes of the Citric Acid Cycle and Electron Transport System in the Large Granule Fraction of Eggs and Trochophores of the Oyster, Crassostrea Virginica

“…drogenase) have been reported to be associated with granules, are reviewed by Brachet (1960). In eggs of the oyster Cleland (1951) has studied oxygen uptake by homogenates in the presence of substrates of the citric acid cycle, and has found that removal of the large granules by centrifugation results in a decreased ability of the homogenates to respire in the presence of such intermediates. In addition, he has shown that succinoxidase and cytochrome oxidase are localized in the large granules.…”