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D Ghosh

Publications and source records attributed to D Ghosh.

At least 163 records · Page 9Linked to original sources
PubMed1994

The refined three-dimensional structure of 3 alpha,20 beta-hydroxysteroid dehydrogenase and possible roles of the residues conserved in short-chain dehydrogenases.

BACKGROUND: Bacterial 3 alpha,20 beta-hydroxysteroid dehydrogenase reversibly oxidizes the 3 alpha and 20 beta hydroxyl groups of steroids derived from androstanes and pregnanes. It was the first short-chain dehydrogenase to be studied by X-ray crystallography. The previous description of the structure of this enzyme, at 2.6 A resolution, did not permit unambiguous assignment of several important groups. We have further refined the structure of the complex of the enzyme with its cofactor, nicotinamide adenine dinucleotide (NAD), and solvent molecules, at the same resolution. RESULTS: The asymmetric unit of the crystal contains four monomers, each with 253 amino acid residues, 38 water molecules, and 176 cofactor atoms belonging to four NAD molecules--one for each subunit. The positioning of the cofactor molecule has been modified from our previous model and is deeper in the catalytic cavity as observed for other members of both the long-chain and short-chain dehydrogenase families. The nicotinamide-ribose end of the cofactor has several possible conformations or is dynamically disordered. CONCLUSIONS: The catalytic site contains residues Tyr152 and Lys156. These two amino acids are strictly conserved in the short-chain dehydrogenase superfamily. Modeling studies with a cortisone molecule in the catalytic site suggest that the Tyr152, Lys156 and Ser139 side chains promote electrophilic attack on the (C20-O) carbonyl oxygen atom, thus enabling the carbon atom to accept a hydride from the reduced cofactor.

Amino Acid Sequence↗
PubMed1994

Monomeric and dimeric forms of cholesterol esterase from Candida cylindracea. Primary structure, identity in peptide patterns, and additional microheterogeneity.

Cholesterol esterase from Candida cylindracea was separated into two fractions, corresponding to a dimeric and a monomeric form. Fingerprint analysis after lysine cleavages shows identical patterns, suggesting lack of primary differences. Crystals obtained from the two proteins differ and suggest the possibility of an equilibrium between the two forms, influenced by the substrate cholesterol linoleate, which appears to stabilize the more active, dimeric form. All crystals have dimers as the asymmetric unit. The primary structure of the enzyme was determined at the peptide level and shows only one difference, Leu-350 instead of Ile, from a DNA-deduced amino acid sequence, and conservation of features typical for cholesterol esterases characterized.

Amino Acid Sequence↗
PubMed1994

Luteal phase ovarian oestrogen is not essential for implantation and maintenance of pregnancy from surrogate embryo transfer in the rhesus monkey.

The aim of this study was to investigate whether luteal phase ovarian oestrogen is required for blastocyst implantation and pregnancy maintenance in the rhesus monkey. Preimplantation embryos were retrieved from naturally ovulated, mated embryo donor monkeys. In group I, developmentally normal, age- and stage-matched embryos were transferred to recipient monkeys showing naturally synchronized ovulatory cycles. Immediately prior to embryo transfer, recipients were subjected to bilateral ovariectomy, and following transfer they were treated with i.m. injections of either progesterone (group Ia, n = 4), or oestradiol + progesterone (group Ib, n = 2). Recipient monkeys of group Ic (n = 4) were subjected to sham ovariectomy and vehicle injection. In group Ia, progesterone supplementation alone led to three pregnancies and live births. In group Ib, there was one live birth. In the control group Ic, four transfers resulted in two live births and one abortion on cycle day 58. Analysis of serum progesterone and oestradiol profiles showed that oestradiol had declined to undetectable levels within 3-5 days after ovariectomy in group Ia recipients, and the area under the curve of serum oestrogen concentrations during the peri-implantation period (days 10-20 after ovulation) were less (P < 0.001) in group Ia compared with group Ic. There were no changes in the area under the curve among serum progesterone concentrations in all the subgroups. In group II, long-term ovariectomized embryo recipients (n = 4) were primed with oestradiol till cycle day 11 of simulated transfer cycle, and received progesterone treatment from cycle day 10 till the end of the experiment.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Effect of thyroidectomy, and thyroxine and alpha 2u-globulin replacement therapy on testicular steroidogenic and gametogenic activities in rats.

Adult male rats were thyroidectomized and killed after 22 days of treatment. Thyroidectomy lowered the weights of testes and accessory sex organs, decreased the activities of testicular delta 5-3 beta- and 17 beta-hydroxysteroid dehydrogenases (HSD), and diminished spermatogenesis, serum levels of testosterone and alpha 2u-globulin. Supplementation with thyroxine at a dose of 5 micrograms/100 g body weight per day for 21 days or supplementation with alpha 2u-globulin at a dose of 1.5 mg/rat per day for 21 days in thyroidectomized animals partially reversed the decrease in HSD activities and serum concentrations of testosterone and alpha 2u-globulin, while spermatogenesis was restored to normal. The weights of testes and accessory sex organs were also reinstated after supplementation with thyroxine or alpha 2u-globulin in thyroidectomized rats in comparison with thyroidectomized animals. It was concluded that alpha 2u-globulin may be an intermediary in the thyroid hormone control of testicular function.

17-Hydroxysteroid Dehydrogenases↗
PubMed1994

Effect of lithium chloride on testicular delta 5-3 beta, 17 beta-hydroxy steroid dehydrogenase, acid phosphatase and gametogenesis in Bufo melanostictus.

Injection of lithium chloride at the dose of 200 micrograms/toad/alternate day for 7, 14 and 21 days caused a significant reduction in the activities of testicular delta 5-3 beta, 17 beta-hydroxysteroid dehydrogenase and acid phosphatase enzymes. There was a marked inhibition in spermatogenesis in lithium chloride treated toad for 14 and 21 days of treatment, but 7 days of treatment has no effect.

17-Hydroxysteroid Dehydrogenases↗
PubMed1994

Luteal phase contraception with mifepristone (RU 486) in the rhesus monkey.

Mifepristone (RU 486), an antiprogesterone, is a promising luteal phase contraceptive agent for human use. However, at present its use is limited by the practical constraint of determining the day of ovulation for an LH + 2 day administration of the drug as indicated from experimental and clinical studies. The aim of the present study was to identify the effective period of luteal phase (luteal phase window) when a single administration of mifepristone would induce antinidatory activity without disturbing menstrual cyclicity and ovulatory pattern in the rhesus monkey. RU 486 (2 mg/kg body weight in benzyl benzoate/olive oil, 1:3) was given to mated monkeys (n = 9) on cycle day 16 in the first treatment cycle (treatment group T1, n = 9), and in the following cycle on cycle day 20 (treatment group T2, n = 8). A single s.c. injection of this antiprogestin during early to midluteal phase (days 1-10 after ovulation, as determined from retrospective analysis of serum concentrations of estrogen and progesterone) provided a one hundred per cent protection against pregnancy, with no apparent side effects. There were no changes in cycle lengths (F = 3.5; P < 0.3), day of ovulation (F = 1.8; P < 0.7) and duration of menses (F = 3.5; P < 0.3) compared with the pre-treatment and post-treatment cycles. Pooled analyses of serum concentrations of estrogen and progesterone during luteal phases of T1 and T2 cycles also showed no variations with those in pre- and post-treatment cycles.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1993

Crystallization and preliminary X-ray diffraction analysis of the complex of human placental 17 beta-hydroxysteroid dehydrogenase with NADP+.

Single crystals of human placental 17 beta-hydroxysteroid dehydrogenase, an enzyme that plays an important role in the interconversion of estrogens, were obtained as the NADP+ complex. These are the first crystals suitable for complete X-ray structure analysis ever reported for a steroid-converting enzyme from a human source. The crystals were grown by vapor diffusion at pH 7.5 with polyethyleneglycol (4000) as the precipitating agent. They have a monoclinic space group C2 and unit cell parameters are a = 123.03 A, b = 45.03 A, c = 61.29 A, and beta = 99.1 degrees. A complete set of diffraction data to 2.9 A has been collected on native crystals.

17-Hydroxysteroid Dehydrogenases↗
PubMed1993

Status of the transcription factors database (TFD).

The Transcription Factors Database is a specialized database focusing on transcription factors and their properties. This report describes the present status of this database and developments during the past year. Within this time, the size of this database has increased by a 2799 total records, and has become accessible through a number of new mechanisms.

Databases, Factual↗
PubMed1993

Three-dimensional model of NAD(+)-dependent 15-hydroxyprostaglandin dehydrogenase and relationships to the NADP(+)-dependent enzyme (carbonyl reductase).

Modelling the amino acid sequence of NAD(+)-linked 15-hydroxyprostaglandin dehydrogenase into the three-dimensional structure of 3 alpha/20 beta-hydroxysteroid dehydrogenase shows that these two enzymes, as well as the NADP(+)-linked prostaglandin dehydrogenase (identical to carbonyl reductase) have similar conformations, in spite of very limited sequence identity (23-28%). Conservation of tertiary structures is greatest over the first two thirds of the polypeptide chains, where the typical NAD+ binding fold is retained, including the five first beta-strands, with only two short deletions or insertions up to residue 147. The remaining thirds of each of the prostaglandin dehydrogenases have significantly different architecture, including insertions that may contribute to enzyme specificity, and, except for an additional helix (alpha G), are difficult to model. Active site relationships can be evaluated and subunit interactions predicted, suggesting that the alpha E + alpha F two-helix surface constitutes the major subunit interacting area, forming a dimeric unit in the oligomeric enzymes.

Amino Acid Sequence↗
PubMed1993

Carboxyethyllysine in a protein: native carbonyl reductase/NADP(+)-dependent prostaglandin dehydrogenase.

Two different forms of the monomeric NADP(+)-linked prostaglandin dehydrogenase/carbonyl reductase were purified from human placenta and shown to differ by the modification of a lysine residue. The modified and the unmodified proteins were reproducibly recovered in a ratio of approximately 1:3, and both were chemically stable. The modified form was more acidic (pI approximately 7.4 versus pI approximately 7.7) but indistinguishable from the unmodified form in specificity and activity. Amino acid analysis, sequence analysis, mass spectrometry, and chemical synthesis identified the modified residue as N6-(1-carboxyethyl)lysine with C-2 of propionic acid attached to the side-chain N of Lys-238. This compound can be formed from the lysine residue and pyruvate via a Schiff base and subsequent reduction. The enzyme and its NAD(+)-dependent counterpart are distantly related (23% residue identity) and have the same family assignment to short-chain dehydrogenases. Alignments and model-building into the tertiary structure of 3 alpha/20 beta-hydroxysteroid dehydrogenase show that carbonyl reductase has an extra loop (positions 149-189) that forms a separate extension and replaces a backbone C-terminal beta-strand. This change affects the substrate pocket, explaining the different substrate specificities but conserves residues of known functional importance. Carboxyethyllysine at position 238 corresponds to a proteolysis-sensitive position in several short-chain dehydrogenases, less well-defined in the model but close to a surface, and is compatible with the accessibility and enzyme properties observed.

Alcohol Oxidoreductases↗
PubMed1993

17 beta-Hydroxysteroid dehydrogenase activity of ovary and hepatopancreas of freshwater prawn, Macrobrachium rosenbergii: relation to ovarian condition and estrogen treatment.

The activity of 17 beta-hydroxysteroid dehydrogenase (17 beta-HSD) was determined in the hepatopancreas and the ovary of freshwater prawn Macrobrachium rosenbergii, at different stages of life. A uniform level of 17 beta-HSD activity was observed in the hepatopancreas of immature, maturing, matured, and gravid prawns, whereas the activity of this enzyme was found to be higher in the ovary of the maturing prawn only. Gradual increases in the GSI values and ovarian protein content at the different stages of maturity were observed in this animal. Between the two organs, higher activity of 17 beta-HSD was observed in the hepatopancreas of the prawn in the maturing stage. The estradiol-17 beta (E2) level measured by radioimmunoassay showed its peak in both the hemolymph (126.0 +/- 7.0 pg/ml) and the ovary (300.00 +/- 9.0 pg/mg protein) in the maturing prawn only compared to that in immature, matured, and gravid prawns. The hormone level became undetectable in the hemolymph and remained about 10-fold less (30.6 +/- 5.0 pg/mg protein) in the ovary of the gravid prawn in comparison to the prawns in the maturing stage. A parallelism between the nature of 17 beta-HSD activity and the hormone level was observed in the ovary at different stages of life. A dose-dependent stimulation of 17 beta-HSD activity was observed in the hepatopancreas of the maturing prawn after three consecutive injections of 0.25, 0.5, 1.0, and 2.0 micrograms/g of estradiol-17 beta (E2) on the 4th day of treatment compared to the control values.(ABSTRACT TRUNCATED AT 250 WORDS)

17-Hydroxysteroid Dehydrogenases↗