The Apparent Shift in Distribution of Aromatase Activity in the Subcellular Fraction of Human Term Placenta Stored At -96°C

Tochigi, Buichi; Osawa, Yosuke

doi:10.1080/07435808609035430

Cited by 6 publications

(4 citation statements)

References 11 publications

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“…Prolonged freezing, possibly in combination with subsequent thawing, apparently disrupted the association of ASPA with myelin by an as-yet-undetermined mechanism. Similar shifts in subcellular distribution have been reported for other membrane proteins following prolonged freezing of brain (Stahl and Swanson 1975) and other tissue (Tochigi et al 1986). However, it may be noted that the association of ASPA with myelin from unfrozen brain proved strong enough to survive treatment with 0.5 mol/L NaCl and 0.1% Na-taurocholate ( Fig.…”

Section: Discussionsupporting

confidence: 83%

“…Prolonged freezing, possibly in combination with subsequent thawing, apparently disrupted the association of ASPA with myelin by an as‐yet‐undetermined mechanism. Similar shifts in subcellular distribution have been reported for other membrane proteins following prolonged freezing of brain (Stahl and Swanson 1975) and other tissue (Tochigi et al. 1986).…”

Section: Discussionsupporting

confidence: 82%

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Bimodal occurrence of aspartoacylase in myelin and cytosol of brain

Wang¹,

Matalon²,

Bhatia³

et al. 2006

Journal of Neurochemistry

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The growing use of N-acetylaspartate as an indicator of neuronal viability has fostered interest in the biological function(s) of this unusual amino acid derivative. In considering the various physiological roles that have been proposed for this relatively abundant molecule one is obliged to take into account its unusual metabolic compartmentalization, according to which synthesis and storage occur in the neuron and hydrolytic cleavage in the oligodendrocyte. The latter reaction, catalyzed by aspartoacylase (ASPA), produces acetyl groups plus aspartate and has been proposed to occur in both soluble and membranous subfractions of white matter. Our study supports such bimodal occurrence and we now present immunoblot, proteomic, and biochemical evidence that the membrane-bound form of ASPA is intrinsic to purified myelin membranes. This was supported by a novel TLC-based method for the assay of ASPA. That observation, together with previous demonstrations of numerous lipid-synthesizing enzymes in myelin, suggests utilization of acetyl groups liberated by myelin-localized ASPA for lipid synthesis within the myelin sheath. Such synthesis might be selective and could explain the deficit of myelin lipids in animals lacking ASPA.

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Section: Discussionsupporting

confidence: 83%

Section: Discussionsupporting

confidence: 82%

Bimodal occurrence of aspartoacylase in myelin and cytosol of brain

Wang¹,

Matalon²,

Bhatia³

et al. 2006

Journal of Neurochemistry

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“…Placental aromatase activity (2.8 ± 0.5 pmol/min.mg) is comparable to activities reported for other mammals but is only 10% of the values found in human term placentae. Tochigi et al [1986] reported aromatase activity ranging from 39-51 pmol/min.mg in homogenates of human placentae. Both sheep (1.4 pmol/min.mg) [France et al, 1987] and pig (5.4 pmol/min.mg) [Corbin et al, 1995] aromatase activities in placental homogenates are in the same range as the primate values reported here.…”

Section: Discussionmentioning

confidence: 99%

Monitoring pregnancy in twinning pygmy loris (Nycticebus pygmaeus) using fecal estrogen metabolites

et al. 1999

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Estrone and estrone conjugates were measured in the feces of three female pygmy lorises (Nycticebus pygmaeus) throughout estrus, pregnancy, and the postpartum period. Two females gave birth to twins, while the third had a single stillborn. A comparison between the hormonal profiles of these three pregnancies with each other and with previously reported pregnancies resulting in singletons or twins [Jurke et al., American Journal of Primatology 41:103–115, 1997] revealed a characteristic pattern of hormonal excretion. This report adds data to and confirms previous claims that monitoring estrone in this species provides a tool to assess gestation length (via determination of estrus period) and to predict the date of parturition and the number of offspring. However, there was an exceptional case of a pregnancy which had the hormonal appearance of a twin pregnancy but resulted in a single stillborn infant. This case prompted us to search for new insights into the characteristics and the origin of the estrogens that are excreted into the feces. Aromatase activity was evaluated in five partial placentae. Am. J. Primatol. 46:173–183, 1998. © 1998 Wiley‐Liss, Inc.

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“…Therefore, the pelleted fraction was used in subsequent experiments. Although lower in specific activity, the 900 x g pellet contained most of the aromatase activity of human term placenta (29). The concentration-dependent inhibition by 60-BrA was then investigated.…”

Section: Resultsmentioning

confidence: 99%

Stereochemistry of the Functional Group Determines the Mechanism of Aromatase Inhibition by 6-Bromoandrostenedione*

Osawa

Coon

1987

Endocrinology

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A selective inhibitor of aromatase (estrogen synthetase) would be a useful pharmacological tool with potential therapeutic application. We have found that 6 alpha-bromoandrostenedione (6 alpha-BrA) is a competitive inhibitor of human placental aromatase with respect to androstenedione, with an apparent Ki of 3.4 nM, while 6 beta-BrA is a mechanism-based irreversible inhibitor with an apparent Ki of 0.8 microM and a kinact of 0.025 min-1. Aromatase activity was measured by tritium release into water from the 1 beta position of [1(-3)H,4(-14)C]androstenedione in reaction mixtures containing NADPH and the aromatase. Time-dependent inhibition was assessed by preincubation of inhibitors with either the 900 X g placental pellet or placental microsomes in the presence of NADPH. Aliquots were taken at intervals, diluted, and assayed for aromatase activity with androstenedione and additional NADPH. The time-dependent inhibition by 6 beta-BrA was dependent on the concentration of this compound and the presence of NADPH, while the addition of excess substrate in the preincubation mixture hindered the inactivation. Both epimers were ineffective in inhibiting rabbit liver microsomal drug-metabolizing activities in a competitive or time-dependent manner. This indicates a high selectivity of 6-BrA inhibition among P-450 cytochromes. These and other 6-substituted androgens may be useful probes into the nature of the active site and mechanism of action of aromatase.

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The Apparent Shift in Distribution of Aromatase Activity in the Subcellular Fraction of Human Term Placenta Stored At -96°C

Cited by 6 publications

References 11 publications

Bimodal occurrence of aspartoacylase in myelin and cytosol of brain

Bimodal occurrence of aspartoacylase in myelin and cytosol of brain

Monitoring pregnancy in twinning pygmy loris (Nycticebus pygmaeus) using fecal estrogen metabolites

Stereochemistry of the Functional Group Determines the Mechanism of Aromatase Inhibition by 6-Bromoandrostenedione*

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