Biochemical Characterization of Recombinant UDP-Glucose:Sterol 3-O-Glycosyltransferase from Micromonospora rhodorangea ATCC 31603 and Enzymatic Biosynthesis of Sterol-3-O-β-Glucosides

A uridine diphosphate-glucose:sterol glycosyltransferase-encoding gene was isolated and cloned from the established fosmid library of Micromonospora rhodorangea ATCC 27932 that usually produces the aminoglycoside antibiotic geneticin. The gene consists of 1,185 base pairs and encodes a 41.4 kDa protein, which was heterologously expressed in Escherichia coli BL21(DE3). In silico analyses of the deduced gene product suggested that it is a member of the family 1 glycosyltransferases. The recombinant protein MrSGT was able to catalyze the transfer of a glucosyl moiety onto the C-3 hydroxy function in sterols (β-sitosterol, campesterol, and cholesterol), resulting in the corresponding steryl glucosides (β-sitosterol-3-O-β-D-glucoside, campesterol-3-O-β-D-glucoside, and cholesterol-3-O-β-D-glucoside). This enzyme prefers phytosterols to cholesterol, and also shows substrate flexibility to some extent, in that it could recognize a number of acceptor substrates.

Istamycin aminoglycosides profiling and their characterization in Streptomyces tenjimariensis ATCC 31603 culture using high-performance liquid chromatography with tandem mass spectrometry

A high-performance liquid chromatography with electrospray ionization ion trap tandem mass spectrometry method was developed and validated for the robust profiling and characterization of biosynthetic congeners in the 2-deoxy-aminocyclitol istamycin pathway, from the fermentation broth of Streptomyces tenjimariensis ATCC 31603. Gradient elution on an Acquity CSH C₁₈ column was performed with a gradient of 5 mM aqueous pentafluoropropionic acid and 50% acetonitrile. Sixteen natural istamycin congeners were profiled and quantified in descending order; istamycin A, istamycin B, istamycin A₀ , istamycin B₀ , istamycin B₁ , istamycin A₁ , istamycin C, istamycin A₂ , istamycin C₁ , istamycin C₀ , istamycin X₀ , istamycin A₃ , istamycin Y₀ , istamycin B₃ , and istamycin FU-10 plus istamycin AP. In addition, a total of five sets of 1- or 3-epimeric pairs were chromatographically separated using a macrocyclic glycopeptide-bonded chiral column. The lower limit of quantification of istamycin-A present in S. tenjimariensis fermentation was estimated to be 2.2 ng/mL. The simultaneous identification of a wide range of 2-deoxy-aminocyclitol-type istamycin profiles from bacterial fermentation was determined for the first time by employing high-performance liquid chromatography with tandem mass spectrometry analysis and the separation of istamycin epimers.

Kinetic studies on recombinant UDP-glucose: sterol 3-O-β-glycosyltransferase from Micromonospora rhodorangea and its bioconversion potential

Kinetics of a recombinant uridine diphosphate-glucose: sterol glycosyltransferase from Micromonospora rhodorangea ATCC 27932 (MrSGT) were studied using a number of sterols (including phytosterols) as glycosyl acceptors. The lowest K m value and the highest catalytical efficiency (k cat/K m) were found when β-sitosterol was the glycosyl acceptor in the enzymatic reaction. In contrast to the enzyme's flexibility toward the glycosyl acceptor substrate, this recombinant enzyme was highly specific to uridine diphosphate (UDP)-glucose as the donor substrate. Besides, the UDP-glucose-dependent MrSGT was able to attach one glucose moiety specifically onto the C-3 hydroxyl group of other phytosterols such as fucosterol and gramisterol, yielding stereo-specific fucosterol-3-O-β-D-glucoside and gramisterol-3-O-β-D-glucoside, respectively. Based on kinetic data obtained from the enzyme's reactions using five different sterol substrates, the significance of the alkene (or ethylidene) side chains on the C-24 position in the sterol scaffolds was described and the possible relationship between the substrate structure and enzyme activity was discussed. This is the first report on the enzymatic bioconversion of the above two phytosteryl 3-O-β-glucosides, as well as on the discovery of a stereospecific bacterial SGT which can attach a glucose moiety in β-conformation at the C-3 hydroxyl group of diverse sterols, thus highlighting the catalytic potential of this promiscuous glycosyltransferase to expand the structural diversity of steryl glucosides.

Characterization of fortimicin aminoglycoside profiles produced from Micromonospora olivasterospora DSM 43868 by high-performance liquid chromatography-electrospray ionization-ion trap-mass spectrometry

In this study, an efficient high-performance liquid chromatography (HPLC)-electrospray ionization (ESI)-ion trap-tandem mass spectrometry (MS/MS) was developed for the identification of the biosynthetic congeners involved in the aminocyclitol aminoglycosidic fortimicin pathway from Micromonospora olivasterospora fermentation. The usage of both acid extraction (pH ∼2.5) followed by an cationic-exchanging SPE cleanup and pentafluoropropionic acid mediated ion-pairing chromatography with ESI-ion trap-MS/MS detection was determined to be sufficiently practical to profile the fortimicin (FOR) congeners produced in a culture broth. The limit of the quantification for the fortimicin A (FOR-A) standard spiked in the culture broth was ∼1.6 ng mL(-1). The average recovery rate was 93.6%, and the intra- and inter-day precisions were <5% with accuracy in the range from 87.1 to 94.2%. Moreover, the epimeric mixtures including FOR-KH, FOR-KR, and FOR-B were separately resolved through a macrocyclic glycopeptide (teicoplanin)-bonded chiral column. As a result, ten natural FOR pseudodisaccharide analogs were identified and semi-quantified in descending order as follows: FOR-A, FOR-B, DCM, FOR-KH plus FOR-KR, FOR-KK1, FOR-AP, FOR-KL1, FOR-AO, and FOR-FU-10. This is the first report on both the simultaneous characterization of diverse structurally closely related FORs derived from bacterial fermentation using HPLC-ESI-ion trap-MS/MS analysis and the chromatographic separation of the three FOR epimers.

Structural characterization of cyclosporin A, C and microbial bio-transformed cyclosporin A analog AM6 using HPLC-ESI-ion trap-mass spectrometry

Cyclosporin A (CyA), a cyclic undecapeptide produced by a number of fungi, contains 11 unusual amino acids, and has been one of the most commonly prescribed immunosuppressive drugs. To date, there are over sixty different analogs reported as congeners and analogs resulting from precursor-directed biosynthesis, human CYP-mediated metabolites, or microbial bio-transformed analogs. However, there is still a need for more structurally diverse CyA analogs in order to discover new biological potentials and/or improve the physicochemical properties of the existing cyclosporins. As a result of the complexity of the resulting mass spectrometric (MS) data caused by its unusual amino acid composition and its cyclic nature, structural characterization of these cyclic peptides based on fragmentation patterns using multiple tandem MS analyses is challenging task. Here, we describe, an efficient HPLC-ESI-ion trap MS(n) (up to MS(8)) was developed for the identification of CyA and CyC, a (Thr(2))CyA congener in which L-aminobutyric acid (Abu) is replaced by L-threonine (Thr). In addition, we examined the fragmentation patterns of a CyA analog obtained from the cultivation of a recombinant Streptomyces venezuelae strain fed with CyA, assigning this analog as (γ-hydroxy-MeLeu(6))CyA (otherwise, known as an human CYP metabolite AM6). This is the first report on both the MS(n)-aided identification of CyC and the structural characterization of a CyA analog by employing HPLC-ESI-ion trap MS(n) analysis.

Biotransformation of rosamicin antibiotic into 10,11-dihydrorosamicin with enhanced in vitro antibacterial activity against MRSA

A biotransformation approach using microbes as biocatalysts can be an efficient tool for the targeted modification of existing antibiotic chemical scaffolds to create previously uncharacterized therapeutic agents. By employing a recombinant Streptomyces venezuelae strain as a microbial catalyst, a reduced macrolide, 10,11-dihydrorosamicin, was created from rosamicin macrolide. Its chemical structure was spectroscopically elucidated, and the new rosamicin analog showed 2-4-fold higher antibacterial activity against two strains of methicillin-resistant Staphylococcus aureus compared with its parent rosamicin. This kind of biocatalytic approach is able to expand existing antibiotic entities and can also provide more diverse therapeutic resources.

Regio-selectively reduced streptogramin A analogue, 5,6-dihydrovirginiamycin M1 exhibits improved potency against MRSA

A newly reduced macrocyclic lactone antibiotic streptogramin A, 5,6-dihydrovirginiamycin M1 was created by feeding virginiamycin M1 into a culture of recombinant Streptomyces venezuelae. Its chemical structure was spectroscopically elucidated, and this streptogramin A analogue showed twofold higher antibacterial activities against methicillin-resistant Staphylococcus aureus (MRSA) compared with its parent molecule virginiamycin M1. Docking studies using the model of streptogramin A acetyltransferase (VatA) suggested that the newly generated analogue binds tighter with overall lower free energy compared with the parent molecule virginiamycin M1. This hypothesis was validated experimentally through the improvement of efficacy of the new analogue against MRSA strains. The biotransformation approach presented herein could have a broad application in the production of reduced macrocyclic molecules.

Changes in body composition as determinants of longitudinal changes in bone mineral measures in 8 to 26-year-old female twins

Between 1990 and 1998, we conducted a longitudinal study of 286 female twins aged 8 to 25 years at baseline (60 monozygotic (MZ) pairs, 44 dizygotic (DZ) pairs and 78 unpaired twins), measured on average 2.4 times (range 2-6) with an average of 1.8 years between measurements (range 0.7-6.7 years). Areal bone mineral density (ABMD) at the lumbar spine, total hip and femoral neck, total body bone mineral content (BMC), total body soft tissue composition (lean mass and fat mass) were measured by dual-energy X-ray absorptiometry, and height and menarchial status were also recorded. Median annual changes in height were negligible at 4 years post-menarche. During the 'linear growth' period up to 4 years post-menarche, ABMD at the lumbar spine, total hip and femoral neck increased with annual change in lean mass by 1.7 (S.E.0.1), 1.4 (0.1) and 1.0 (0.1) percent per kilogram per year, respectively (all p<0.001), independently of changes in fat mass or height. During the 'post-linear growth' period, ABMD at the total hip and femoral neck increased with annual change in fat mass by 0.3 (0.1) and 0.5 (0.1) percent per kilogram per year (all p < 0.01), independent of change in lean mass. Annual changes in total body BMC were associated with annual changes in lean mass (1.9 (0.2) percent per kilogram), in fat mass (1.3 (0.2) percent per kilogram) and in height (0.7) (0.2) percent per centimeter) during linear growth, and in fat mass (1.0 (0.1)) and lean mass (0.6 (0.1)) percent per kilogram post-linear growth (all p < 0.001). We conclude that changes in bone mineral measures are strongly associated with changes in lean mass during linear growth, while post-linear growth, changes in fat mass are the predominant, although weaker, predictor. These findings suggest that the strong cross-sectional association between bone mineral measures and lean mass is established during growth and development, and that fat mass emerges as a more powerful determinant of bone change in healthy adult females.

Analysis of longitudinal data from twins

Longitudinal data from twin pairs may be used to determine how the genetic effects influencing a quantitative trait change with age. Here a model for mixed longitudinal data of Huggins and Loesch [1998] on unrelated individuals is extended to twin studies. The model is fitted using robust statistical methods and a bootstrap procedure is proposed to estimate the percentiles. The method is applied to longitudinal twin data on body mass index in male and female twin pairs aged 5-18 years.

Genetic correlates of menarcheal age: a multivariate twin study

Multivariate genetic models were fitted to data from 44 pairs of MZ and 42 pairs of DZ twin girls on weight, height, and skeletal maturation at the age of menarche, in order to obtain information on genetic relationships of those measures with the age of menarche. The relationships of all three physical measures with this age were largely genetically controlled, but a genetic system controlling skeletal maturity was identified as the only genetic determinant of menarcheal age, independent of those systems of the two remaining physical measures. Heritabilities of all individual traits considered in the study were uniformly high. Possible links of genetic information with hormonal functions determining menarche are discussed.

Growth in stature in fragile X families: a mixed longitudinal study

The effect of fragile X on growth in stature was estimated in individuals aged 5-20 years from 50 fragile X families. The multivariate normal model for pedigree analysis was applied to the mixed longitudinal data, which varied with regard to intervals between the measurements and their number in individual subjects, totalling 349 measurement data points from fragile X families, and 292 data points from unrelated normal subjects. The results of genetic and regression analysis showed that, in fragile X boys and girls, total pubertal height gain is impaired, whereas the rate of growth during the preadolescent period is increased, compared with the growth rate of nonfragile X subjects. Moreover, the growth parameters in fragile X males were found to be correlated with the size of CGG trinucleotide expansion. The hypothesis of premature activation of the hypothalamo-pituitary gonadal axis is postulated as the cause of growth impairment in fragile X boys and girls, which should be verified by data on the timing of pubertal stages, hormone levels, and bone maturation.

[Plasminogen activator inhibitor 1--a new thrombosis risk marker]

The plasma activity of plasminogen activator inhibitor 1 (PAI-1) was measured in 278 clinically healthy subjects (98 men, 180 women; mean age 26 [18-50] years). In 198 of them there were factors increasing the risk of thrombosis, such as smoking, over-weight and/or oral contraceptives. PAI-1 activity was within normal range (less than 4 U/ml) in male nonsmokers of normal weight and in female nonsmokers not taking oral contraceptives. In male smokers (5.76 +/- 1.93 U/ml) and in overweight subjects of both sexes (7.49 +/- 1.87 U/ml) PAI-1 was increased up to 10.6 U/ml as an indication of decreased fibrinolysis capacity. Nonsmoking females on oral contraceptives had lower PAI-1 levels (2.72 +/- 0.86 U/ml) than nonsmokers without hormonal intake (3.21 +/- 1.03 U/ml; P less than 0.001). Apparently the increased risk of thrombosis that occurs on oral contraceptives is not due to increased PAI-1 activity.