Kinetics, stoichiometry, and identification of the reactive thiolate in the inactivation of UDP-GlcNAc enolpyruvoyl transferase by the antibiotic fosfomycin

Fosfomycin [(1R,2S)-1,2-epoxypropylphosphonic acid] has been shown to exert its antibiotic effect through the inhibition of UDP-GlcNAc enolpyruvoyl transferase [Kahan, F. M., et al. (1974) Ann. N.Y. Acad. Sci. 235, 364], the enzyme responsible for catalyzing the first committed step in bacterial cell wall biosynthesis. Time-dependent inactivation of MurZ by fosfomycin was found to be greatly accelerated by the presence of cosubstrate UDP-GlcNAc but could also be speeded appreciably by the unreactive substrate analog 3-deoxy-UDP-GlcNAc. These results argue against a reaction-based participation of the cosubstrate and suggest that UDP-GlcNAc has a role in influencing active site conformation critical to the inactivation event. A study of the influence of UDP-GlcNAc and fosfomycin on the kinetics of inactivation allowed the determination of dissociation constants for fosfomycin (KF = 8.6 microM) and UDP-GlcNAc (KS = 14 microM), in addition to a limiting inactivation rate constant (k(inact) = 7.4 min-1) at saturating UDP-GlcNAc and fosfomycin concentrations. Mass spectrometry of inactivated MurZ demonstrated an increase in molecular weight of 138, consistent with the covalent addition of a molar equivalent of fosfomycin (136 kDa). Titration of MurZ with fosfomycin revealed a stoichiometry of 1 molecule of inhibitor per active site when assessed using either enzyme activity or mass spectrometry as an index of modification. Peptide mapping of tryptic digests of fosfomycin-inactivated MurZ revealed modification of a unique 41-mer, the sequence of which revealed that Cys115 was the site of attachment of fosfomycin.

Cloning, overexpression and isolation of the type II FDP aldolase from E. coli for specificity study and synthetic application

A stable overexpression E. coli strain containing the plasmid pKEN 2 for the production of the Zn(2+)-dependent FDP aldolase from E. coli has been developed. Approximately 14,000 U of the enzyme (specific activity = 23.3 U/mg) can be obtained from 4-L of growth medium. The enzyme was isolated, purified to homogeneity and used for the studies of stability, substrate specificity and metal ion replacement and dissociation. Crystals of the enzyme have been obtained for structural analysis. This E. coli strain was deposited with the American Type Culture Collection (ATCC #77472).

Nifedipine-induced analgesia after epidural injection in rats

We explored the analgesic effect of epidural nifedipine in male Sprague-Dawley rats. By using an implanted epidural catheter, the rats were given 35 microL of dimethylsulfoxide (DMSO) alone or DMSO containing 2.5, 5, 10, or 20 microM of nifedipine. Analgesia was measured by tailflick (TF) involving spinal reflexes, and by hotplate (HP) requiring an intact central nervous system. The latencies were recorded up to 120 min after the injection. The cutoff time of the noxious stimuli was 20 s in the TF and 60 s in the HP to prevent tissue damage. The TF technique revealed a significant difference from the control at doses of 5, 10, and 20 microM with no difference among the groups. Maximum latencies (cutoff time) lasted for 15, 30, and 40 min at doses of 5, 10, and 20 microM, respectively. The HP technique disclosed a dual effect: a significant decrease at the dose of 2.5 microM, no effect at 5 microM, and an increase at 10 and 20 microM. However, the median latency did not reach the cutoff time. We conclude that nifedipine, given epidurally, possesses antinociceptive properties at the dose of 5 microM and higher, detected better by the TF than HP. Our data suggest that the antinociceptive effect of nifedipine, at the studied doses, is more prominent at the spinal than the supraspinal level.

Mammographic changes in postmenopausal women undergoing hormonal replacement therapy

Increasing numbers of postmenopausal women are undergoing hormonal replacement therapy. In this pictorial essay, we present the spectrum of mammographic changes seen in these women. These changes include symmetric and asymmetric increase in breast density, increase in size of fibroadenomas, and development or increase in size of cysts. Our examples illustrate that differentiation of hormonal therapy changes from neoplasm can occasionally be problematic when a focal density or mass is seen on mammograms. Furthermore, reexamination of published reports and our cases suggests that treatment with estrogen alone promotes enlargement of cysts and fibroadenomas, whereas treatment with a combination of estrogen and progesterone is more likely to be associated with diffuse increase in density.

Diagnosis of appendicitis: imaging findings in patients with atypical clinical features

Acute appendicitis is usually diagnosed on the basis of signs, symptoms, and results of simple laboratory tests. However, in patients with atypical clinical features, imaging studies play a significant role in preoperative diagnosis and determination of proper treatment. In this pictorial essay, we present a spectrum of imaging findings in patients whose clinical features were unusual because of the abnormal position of the appendix, the presence of other illnesses, or the presence of complications in children. Appendicitis was not initially considered on clinical presentation in any of our cases. In most cases, the correct diagnosis of appendicitis was made or, at least in retrospect, could have been made on the basis of imaging findings.

Lumbar extradural morphine and caudal extradural morphine for postoperative analgesia and their adverse effects

The efficacy of morphine by either lumbar extradural route or caudal extradural route and their adverse effects for postoperative analgesia were studied by comparing with the control group without morphine administration. 105 patients, 79 males and 26 females, aged 18 to 70 years, scheduled for hemorrhoidectomy surgery were selected. They were randomly assigned into three groups, i.e group I: without morphine use as control group (n = 35), group II: lumbar extradural morphine group (n = 35) and group III: caudal extradural morphine group (n = 35). Patients in group I received general anesthesia by face mask after induction by intravenous anesthetics and maintained with potent halogenated inhalation agents (isoflurane) through face mask. Patients in group II received lumbar extradural blockade through the L4-L5 intervertebral space, and those in group III received caudal extradural blockade through the sacrococcygeal junction (sacral hiatus) for intraoperative anesthesia and analgesia. Drugs included 0.5% bupivacaine 10ml + 2% xylocaine 10ml + 2mg morphine HCl + 0.1mg epinephrine were given either into the lumbar extradural space or into the caudal extradural space. No more narcotic has been given throughout the whole intraoperative course. All of these patients were followed up 24 hours later after the end of anesthesia. There were 11 patients (31.4%) in the control group, 26 patients (74.3%) in the lumbar extradural morphine group, and 25 patients (71.4%) in the caudal extradural morphine group who did not need additional narcotic for pain relief for more than 24 hours postoperatively.(ABSTRACT TRUNCATED AT 250 WORDS)

Development of selective tight-binding inhibitors of leukotriene A4 hydrolase

Leukotriene A4 hydrolase is a zinc-containing enzyme which exhibits both epoxide hydrolase and aminopeptidase activities. Since the enzyme product leukotriene B4 is an inflammatory mediator, it is of interest to develop selective inhibitors of leukotriene A4 hydrolase as potential antiinflammatory agents and as mechanistic probes. A systematic study on the enzyme specificity and the inhibition of its amidase activity with more than 30 synthetic inhibitors has led to the development of an alpha-keto-beta-amino ester (26) and a thioamine (27) as tight-binding, competitive type transition-state analog inhibitors of the aminopeptidase activity, with Ki values of 46 and 18 nM, respectively. Both compounds also inhibit the epoxide hydrolase activity, with the IC50 values of 1 microM and 0.1 microM for 26 and 27, respectively.

An antinociceptive effect of the intraperitoneal injection of nifedipine in rats, measured by tail-flick test

The tail-flick (TF) technique was used to assess the antinociceptive properties of nifedipine (NIF) given intraperitoneally (i.p.). First, the most suitable intensity of the noxious stimulus (temperature of the bulb) has been ascertained and used in the main study. Male Sprague-Dawley rats received NIF, dissolved in dimethyl sulfoxide (DMSO) at the doses of 0.0, 0.5, 2, 5, 10 and 15 mg/kg, or control with no injection. For the main study, the noxious stimulus was limited to 15 sec (cut-off time) and TF latencies were recorded up to 120 min. The antinociceptive response was expressed as the area under the curve for each rat and analyzed by one-way ANOVA. The antinociceptive response to the lower doses of NIF (0.5 and 2 mg/kg) did not differ from control (no injection) and DMSO alone. Significance was found at 5, 10 and 15 mg NIF with no difference among the doses. However, there was an increasing tendency of the mean values from 0.5 to 15 mg NIF resulting in a positive correlation. The correlation coefficient was 0.32483 (p = 0.015) and regression equation Y = (19.37) x dose + 1320. Our data suggest that spinal mechanisms are involved in NIF-induced antinociception.

Enzyme-catalyzed oligosaccharide synthesis

Cell-surface carbohydrates and their conjugates are involved in many types of molecular recognition. This review describes recent developments in enzyme-catalyzed oligosaccharide synthesis, with particular focus on glycosyltransferase and glycosidase reactions. With the increasing availability of glycosyltransferases via recombinant DNA technology, glycosyltransferase-catalyzed glycosylation with in situ regeneration of sugar nucleotides appears to be the most effective method for large-scale stereocontrolled oligosaccharide synthesis.

Enzymatic synthesis of (R) and (S) 1-deuterohexanol

This paper describes practical enzymatic procedures for the synthesis of (R) and (S) 1-deuterohexanol, a useful building block for chiral poly isocyanated liquid crystals. Alcohol dehydrogenases from horse liver and Pseudomonas catalyzed the reduction of hexanal with deuterated NAD (NADD) resulting in 50% and 89% yields of (R) and (S) 1-deuterohexanol, respectively. The deuterated cofactor was regenerated in situ by alcohol dehydrogenase catalyzed oxidation of ethanol-d6 or 2-propanol-d8. The (S) alcohol was also synthesized by the horse liver alcohol dehydrogenase reduction of 1-deuterohexanal, which was prepared chemically from hexanal. The yields of the reaction were greatly increased by the use of a biphasic system or with the immobilized enzyme in anhydrous organic solvents. Horse liver alcohol dehydrogenase was stabilized by immobilization on PAN or noncovalent entrapment on XAD resin.

New developments in enzymatic peptide synthesis

This review article describes new enzymatic methods developed for the efficient and irreversible synthesis of peptides based on native and modified proteases, and for the synthesis of polypeptides containing D- and/or unnatural amino acids. Potential opportunities for future developments in the field based on new enzymes, tailor-made catalytic antibodies, and on the technique of in vitro mutagenesis are also described.

[Prolongation of hyperbaric bupivacaine spinal anesthesia with clonidine]

Recent reports showed that spinal clonidine might provide satisfactory analgesia via a nonopioid mechanism. In this study we tried to evaluate the prolongation of analgesic effect of the hyperbaric bupivacaine spinal anesthesia with clonidine. 40 ASA class I-II patients scheduled for TURP were randomly classified into two groups of 20 each. In saline group, 3 ml 0.5% hyperbaric bupivacaine plus 1 ml normal saline was given. In clonidine group, 1 ml (0.15 mg) clonidine in addition to 3 ml 0.5% bupivacaine was given. All the patients were placed in lateral position and dural puncture was made at the L3-4 interspace using a 25G spinal needle. Assessment of the sensory blockade by "pinprick" and motor blockade by Bromage scale and measurement of blood pressure and heart rate were performed after injection. All data were analyzed by Student's t-test. A p value less than 0.05 was considered statistically significant. Our results showed that the highest sensory blockade level and the time required for maximal spread of the sensory blockade were of no significant difference between groups. The mean time for two segments regression and mean time for regression to L2 were significantly greater in the clonidine group than in the saline group (p less than 0.001). Motor blockade was also prolonged in the clonidine group than the clonidine group. Side effects such as hypotension (10 in clonidine gp vs 4 in saline gp) and bradycardia (4 clonidine gp vs 2 in saline gp) commonly occurred in the clonidine group, but all patients could be effectively treated with ephedrine and atropine respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Sequence and analysis of the rpoN sigma factor gene of rhizobium sp. strain NGR234, a primary coregulator of symbiosis

We report the nucleotide sequence of the rpoN gene from broad-host-range Rhizobium sp. strain NGR234 and analyze the encoded RPON protein, a sigma factor. Comparative analysis of the deduced amino acid sequence of RPON from NGR234 with sequences from other gram-negative bacteria identified a perfectly conserved RPON box unique to RPON sigma factors. Symbiotic regulatory phenotypes were defined for a site-directed internal deletion within the coding sequence of the rpoN gene of Rhizobium strain NGR234: they included quantitative nodulation kinetics on Vigna unguiculata and microscopic analysis of the Fix- determinate nodules of V. unguiculata and Macroptilium atropurpureum. RPON was a primary coregulator of nodulation and was implicated in establishment or maintenance of the plant-synthesized peribacteroid membrane. Phenotypes of rpoN in Rhizobium strain NGR234 could be grouped as symbiosis related, rather than simply pleiotropically physiological as in free-living bacteria such as Klebsiella pneumoniae and Pseudomonas putida.

Intrathecal morphine's effect on somatosensory impulses transmission-studied with posterior tibial nerve SSEP

In order to investigate neurotoxic potential of spinally injected morphine solution, somatosensory evoked potential (SSEP) was utilized to detect the change of electrophysiologic activity of spinal neurons after long term application of intrathecal morphine. Eight patients received intrathecal morphine injection regularly after CHEMO-PORT implantation were studied with posterior tibial nerve SSEP. Patients received SSEP examination just before and right after first episode of morphine injection and were followed up at 30 minutes, 60 minutes, 2 hours, 8 hours, and the 7th day and the third month of regularly injection. The results showed that there were no definite change of latencies and amplitudes of impulses generated by lumbar spinal cord (N22) and cortex (P40). We therefore suggest that electrophysiologic activities of spinal cord and cortex are not affected by chronic intrathecal morphine injection. Possible mechanism and proposed pathway of morphine's action were also discussed.

The depth to the epidural space

Two hundred and ten patients, 145 males and 65 females, aged 20 to 72 years old, ready to receive extracorporeal shock wave lithotripsy under epidural anesthesia were studied to evaluate if any correlation existed between body weight, body surface area, body mass index and body height and the depth to the epidural space. The mean value for the depth to the epidural space was 4.77 +/- 0.55 cm for males, 4.25 +/- 0.55 cm for females and the overall average was 4.61 +/- 0.60 cm. The range of the depth to the epidural space was 3.0-7.0 cm. Linear regression analysis revealed significant correlation between body weight, body surface area, body mass index, body height an the depth to the epidural space, in the order of BW greater than BSA greater than BMI greater than BH. It is concluded that body weight, body surface area, body mass index and body height affect the depth to the epidural space and play an important role in predicting the depth to the epidural space.

Molecular cloning, nucleotide sequence and fine-structural analysis of the Corynebacterium glutamicum fda gene: structural comparison of C. glutamicum fructose-1,6-biphosphate aldolase to class I and class II aldolases

The Corynebacterium glutamicum fda gene encoding fructose-1,6-biphosphate (FBP) aldolase has been isolated by complementation of an Escherichia coli mutant. The nucleotide sequence of a 3371 bp chromosomal fragment containing the C. glutamicum fda gene was determined. The N-terminal amino acid sequence of C. glutamicum FBP aldolase identified the correct initiation site for the fda gene, and a molecular weight of 37,092 was predicted for the fda polypeptide. S1 nuclease mapping identified the transcriptional start site, and Northern hybridization analysis indicated that the fda gene encodes a single 1.3 kb transcript. The primary structure of C. glutamicum FBP aldolase shows strong homology to class II FBP aldolases. Conservation of primary structure was observed between class I and class II aldolases, but several residues essential for catalytic activity in class I aldolases were absent from class II aldolases.

Enzymatic catalysts in organic synthesis

The synthetic value of enzymes is being increasingly recognized. With an understanding of enzyme-catalyzed reactions and the techniques now available for the low-cost production and rational alteration of enzymes and for the design of new enzymatic activities, biocatalytic synthesis should become one of the most valuable synthetic methods. The fundamental as well as the practical issues of this rapidly growing area are described and its impact on the technology pertaining to synthesis is considered.