Endometrial and myometrial tissues, obtained from Merino ewes on 5 different days of the estrous cycle, were incubated at 37 C in 30 ml of gassed (95% O2:5% CO2) Krebs-bicarbonate buffer containing, 0, 10, 100 or 1,000 muU/ml oxytocin. Aliquots of the medium were removed at 10 min intervals and examined for prostaglandin F2alpha (PGF2alpha) content by radioimmunoassay. Fresh-frozen (-70 C) samples of endometrial and myometrial tissue were homogenized in Tyrode's solution. Particulate fractions from each tissue, sedimenting between 1,000 X g for 10 min and 165,000 X g for 30 min, were prepared and assayed for [3H]oxytocin-binding activity. Endometrium incubated in vitro released PGF2alpha spontaneously and oxytocin enhanced this release in a dose-dependent manner. The degree of enhancement with low doses of oxytocin appeared to increase as estrus approached, reaching a maximum on the day of estrus. High-affinity binding sites (Kd = 5 to 7 X 10(-10) M) were found in both myometrium and endometrium. The number of high-affinity sites rose to a peak at estrus in both tissues but the binding capacity of endometrium was twice that of the myometrium at this time. Although both tissues released PGF2alpha during incubation, oxytocin enhanced release from endometrial tissue only. The results suggest that (i) the endometrium is a target for oxytocin, (ii) synthesis of PGF2alpha by the uterus may involve interaction between oxytocin and its endometrial receptors and (iii) ovarian steroids may influence uterine PG synthesis by regulating the availability of these receptors.

No abstract

No abstract

The genes encoding a thermally stable and regio-selective nitrile hydratase (NHase) and an amidase from Comamonas testosteroni 5-MGAM-4D have been cloned and sequenced, and active NHase has been over-produced in Escherichia coli. Maximal activity requires co-expression of a small open reading frame immediately downstream from the NHase beta subunit gene. Compared to the native organism, the E. coli biocatalyst has nearly threefold more NHase activity on a dry cell weight basis, and this activity is significantly more thermally stable. In addition, this biocatalyst converts a wide spectrum of nitrile substrates to the corresponding amides. Such versatility and robustness are desirable attributes of a biocatalyst intended for use in commercial applications.

No abstract

Microbial catalysts having a combination of nitrile hydratase and amidase activities had a significantly-higher specific activity for hydrolysis of 3-hydroxyalkanenitriles than microbial nitrilase catalysts. Comamonas testosteroni 22 ± 1, Dietzia sp. ADL1 and Comamonas testosteroni 5-MGAM-4D nitrile hydratase/amidase biocatalysts each hydrolyzed 3-hydroxyvaleronitrile to 3-hydroxyvaleric acid (as the ammonium salt) in 99 ± 100% yields, but in consecutive batch reactions with catalyst recycle, alginate-immobilized C. testosteroni 5-MGAM-4D had superior enzyme stability and volumetric productivity. In a series of 85 consecutive batch reactions with biocatalyst recycle for the production of 1.0 M 3-hydroxyvaleric acid, the recovered nitrile hydratase and amidase activities in the final reaction were 29% and 40%, respectively, of the initial activities. The catalyst productivity for this series of reactions was 670 g 3-hydroxyvaleric acid/g dry cell weight (50 g 3-hydroxyvaleric acid/g biocatalyst bead), and the volumetric productivity of the initial reaction in the series was 44 g 3-HVA/L/h. Similar results were obtained with alginate-immobilized C. testosteroni 5-MGAM-4D for the hydrolysis of 3-hydroxybutryonitrile and 3-hydroxypropionitrile to the corresponding 3-hydroxyalkanoic acid ammonium salts.

Five- and six-membered ring lactams have been prepared by first converting an aliphatic α,ω-dinitrile to an ω-cyanocarboxylic acid ammonium salt, using a microbial cell catalyst having an aliphatic nitrilase activity (Acidovorax facilis 72W, ATCC 55746) or a combination of nitrile hydratase and amidase activities (Comamonas testosteroni 5-MGAM-4D, ATCC 55744). The ω-cyanocarboxylic acid ammonium salt was then directly converted to the corresponding lactam by hydrogenation in aqueous solution, without isolation of the intermediate ω-cyanocarboxylic acid or ω-aminocarboxylic acid. Only one of two possible lactam products was produced from α-alkyl-substituted α,ω-dinitriles, where the nitrilase of A. facilis 72W regioselectively hydrolyzed only the ω-cyano group to produce a single cyanocarboxylic acid ammonium salt in greater than 98% yield.

The methylotrophic yeast Hansenula polymorpha has been developed as an efficient production system for heterologous proteins. The system offers the possibility to cointegrate heterologous genes in anticipated fixed copy numbers into the chromosome. As a consequence co-production of different proteins in stoichiometric ratios can be envisaged. This provides options to design this yeast as an industrial biocatalyst in procedures where several enzymes are required for the efficient conversion of a given inexpensive compound into a valuable product. To this end recombinant strains have been engineered with multiple copies of expression cassettes containing the glycolate oxidase (GO) gene from spinach and the catalase T (CTT1) gene from S. cerevisiae. The newly created strains produce high levels of the peroxisomal glycolate oxidase and the cytosolic catalase T. The strains efficiently convert glycolate into glyoxylic acid, oxidizing the added substrate and decomposing the peroxide formed during this reaction into water and oxygen.