Studies on pharmacological and biochemical properties of deamino-dicarba-[GLY-7]-oxytocin (Y-5350)

Pharmacological and biochemical properties were investigated on deamino-dicarba-[Gly-7]-oxytocin (Y-5350). This is a newly developed compound, in which the disulfide bond and [Pro-7] of deamino-oxytocin are substituted by an ethylene linkage and glycine respectively. Bioassayed Y-5350 exhibited 202.6 u/mg of oxytocic activity, 4.6 u/mg of avian depressor activity, 441.2 u/mg of rat milk-ejecting activity and 0.02 u/mg of rat antidiuretic activity, however, adepressor activity was also evident in rats. In particular, the diuration of antidiuretic activity was short. Moreover, the oxytocic activity in pregnant rats and rabbits was weak in comparison with oxytocin. Cumulative dose-response studies were carried out on the isolated rat uterus using van Dyke-Hasting solution. The intrinsic activity was the same level as that of oxytocin, and the pD2 value was 8.62. Oxytocic activity was much enhanced by the existence of 0.5 or 2mM magnesium ion in vitro. However, the agreement between in vivo and in vitro oxytocic activity was not complete when assay was carried out in the prescence of 2 mM magnesium ion. Oxytocin was inactivated by the serum of pregnant women. In the experiment using rats, oxytocin was also destroyed by the extracts of uterus, kidney and liver. In contrast, Y-5350 was not destroyed by any of the enzyme solutions mentioned above.

A soluble super-active form of insulin

Insulin-like material can be extracted from insulin-Sepharose. This soluble material elicits super-insulin responses from mammary epithelial cells. It stimulates the accumulation of alpha-aminoisobutyric acid by virgin mouse mammary cells, which are unresponsive to insulin itself. It exerts a greater stimulatory effect on mammary cells from pregnant mice than insulin. It also is more efficacious than insulin as a stimulant of DNA synthesis and the combined activities of glucose-6-phosphate dehydrogenase (EC 1.1.1.49) and phosphogluconate dehydrogenase (EC 1.1.1.43). Its specific biological activity on these cells is more than five times greater than that of insulin.

Spermidine in hormone-dependent differentiation of mammary gland in vitro

Stiulation of milk-protein synthesis in mouse mammary epithelium in vitro requires insulin, hydrocortisone, and prolactin. The requirement for hydrocortisone can be replaced by spermidine. The possibility that spermidine mediates the effect of glucocorticoid is also supported by the observation that the cellular spermidine concentration increases before the accelerated synthesis of casein and alpha-lactalbumin.

Turnover of phospholipids in an unsaturated fatty acid auxotroph of Escherichia coli

The membrane phospholipids of an unsaturated fatty acid auxotroph of Escherichia coli were found to undergo turnover. These phospholipids were excreted into the culture medium, and were replaced in the cell with newly synthesized phospholipids. Phospholipids of growing cells supplemented with elaidic acid underwent rapid turnover, while those of cells supplemented with oleate, or cis-vaccenate plus palmitoleate, underwent slow turnover. Starvation for required amino acids stimulated this turnover in the latter two cases. Protein was also lost from growing cells. However, after amino acid starvation this loss ceased while phospholipid turnover continued. Electron micrographs of growing cells indicated that large pieces of membrane-like material were separating from the cell surface.

Is prolactin mitogenic for mammary epithelium?

Prolactin administration to mature virgin mice leads to prolilferation of epithelium of the mammary gland. In organ culture, prolactin is not mitogenic, but insulin and insulin-free serum are. These observations are reconciled by the finding that insensitive epithelium is sensitized to insulin and/or serum by prolactin treatment in vivo. Thus, it appears that prolactin acts indirectly as a mitogen by rendering the cells susceptible to the aforementioned mitogens.

Degradation of rutin by Aspergillus flavus. Quercetinase: isolation of a low molecular-weight form containing less carbohydrate

Previous work indicated that quercetinase (a flavonol 2,4-dioxygenase) is a glycoprotein with a molecular weight of 111 000 ± 4000 and containing 27.5% carbohydrate. However, a form having a molecular weight of about 80 000 and containing only 4.7% carbohydrate was recovered from two different batches of enzyme that behaved in an anomalous manner on purification. The conditions responsible for bringing about the separation of the carbohydrate moiety from the enzyme appear to result from the combined effect of high salt concentrations on drying in vacuo followed by chromatography on Sephadex G-100. Both forms were enzymatically active, had the same isoelectric point, were similarly affected by inhibitors, and equally stable towards denaturation by heat. The carbohydrate moiety thus is not an integral part of the enzyme.

Degradation of rutin by Aspergillus flavus. Studies on specificity, inhibition, and possible reaction mechanism of quercetinase

The dioxygenase produced by Aspergillus flavus that oxidizes quercetin contains 2 moles of copper per mole of enzyme and binds at least 2 moles of substrate. The enzyme is not inhibited by sulfhydryl reagents or affected by H2O2, but is inhibited by copper-chelating agents and reducing agents. Nitrogen bases with chelating ability are more effective inhibitors than those that do not form metal chelates.The dioxygenase oxidizes flavones that possess a double bond between carbons-2 and -3 and a hydroxyl on carbon-3. Hydroxyls at other positions affect both the relative rates of enzymatic oxidation and the concentration of substrate required to attain half maximal rate (Km). The evidence indicates that the substrate binds to the copper of the enzyme via the 3-hydroxyl and 4-carbonyl groups of the substrate. A possible mechanism for the reaction is presented.

Purification and properties of a phenol carboxylic acid acyl esterase from Aspergillus flavus

Aspergillus flavus produces an extracellular esterase that hydrolyses phenolic carboxylic acid acyl esters. An assay based upon the measurement of the rate of release of phloroglucinol on hydrolysis of the ester of phloroglucinol and protocatechuic acid is described. The most active preparation hydrolyzed 30.8 μmoles of substrate per minute per milligram of protein and was active against a wide range of esters of meta and para hydroxybenzoic acid derivatives.The enzyme was isolated as a homogeneous protein, as judged by ultracentrifugation and by electrophoresis and had an isoelectric point of pH 4.45. The molecular weight was determined as 166 000. The enzyme is a glycoprotein containing 42.8% carbohydrate and the amino acid composition is described.

Insulin-sepharose and the dynamics of insulin action

In terms of the rate of accumulation of alpha-aminoisobutyric acid, mammary epithelial cells from mature virgin mice respond rapidly to insulin covalently bound to sepharose particles, but do not respond initially to soluble insulin in vitro. The response to insulin-sepharose is prevented if the cells are first exposed to insulin. These observations may provide new insight into the dynamics of insulin action.

Degradation of rutin by Aspergillus flavus. Purification of the dioxygenase, querecentinase

Evidence is presented that a single enzyme, quercetinase, is responsible for the degradation of quercetin by Aspergillus flavus to yield carbon monoxide and a depside, 2-protocatechuoylphloroglucinol carboxylic acid. A procedure for the isolation of the dioxygenase as a homogeneous protein is described. The most purified preparation degraded 10 800 μmoles of quercetin/h mg protein and was homogeneous as judged by ultracentrifugation and by electrophoresis. The molecular weight was determined as 111 000 + 4000. Km values for quercetin and oxygen as substrates were 5.2 × 10−6 M and 1.2 × 10−4 M respectively. The enzyme is a glycoprotein containing 27.5% carbohydrate and the amino acid composition is presented.

Development of insulin-sensitivity by mouse mammary gland in vitro

Explants from mammary gland of pregnant mice are sensitive to insulin, but corresponding explants from mature, virgin mice are insensitive to insulin in certain respects. Isolated virgin tissue can acquire insulin-sensitivity independent of exogenous insulin. Some endocrinological and developmental implications are discussed.