E. P. Abraham

Position and Diaphoresis in Acute Asthma

Presence of pulsus paradoxus, PCO2, sternocleidomastoid retraction, and flow rates have been used at the bedside to assess the severity of acute asthma. In our study of 49 adult patients, pulse rate, respiratory rate and pulsus paradoxus were shown to be significantly higher in patients assuming the upright position on admission to the emergency center; arterial pH, PO2, and peak expiratory flow rate were significantly lower in the upright patients. All upright patients had sternocleidomastoid retraction. Peak expiratory flow rate was 73.3 +/- 5 liters per minute in diaphoretic patients, 134 +/- 21 liters per minute in non-diaphoretic, upright patients, and 225 +/- 7.5 liters per minute in recumbent patients (p less than 0.02). No recumbent patient had a peak expiratory flow rate of less than 150 liters per minute or a PCO2 of greater than 44 mm Hg. The index of Fischl, signifying a need for admission to the hospital if greater than 4, was 4 or higher in 70 percent of upright patients and in 88 percent of diaphoretic patients. Only 7 percent of recumbent patients had Fischi indexes of greater than 4.

Acyl coenzyme A: 6‐aminopenicillanic acid acyltransferase from Penicillium chrysogenum and Aspergillus nidulans

A study of the final stages of the biosynthesis of the penicillins in Penicillium chrysogenum has revealed two types of enzyme. One hydrolyses phenoxymethyl penicillin to 6‐aminopenicillanic acid (6‐APA). The other, also obtained from Aspergillus nidulans, transfers a phenylacetyl group from phenylacetyl CoA to 6‐APA. The acyltransferase, purified to apparent homogeneity, had a molecular mass of 40 kDa. It also catalyses the conversion of isopenicillin N (IPN) to benzylpenicillin (Pen G) and hydrolyses IPN to 6‐APA. In the presence of SDS it dissociates, with loss of activity, into fragments of ca 30 and 10.5 kDa, but activity is regained when these fragments recombine in the absence of SDS.

Formation and Properties of Protoplasts from Antibiotic-producing Strains of Penicillium chrysogenum and Cephalosporium acremonium

SUMMARY: Osmotically fragile protoplasts have been prepared by the action of lytic enzymes on the mycelium of Penicillium chrysogenum and Cephalosporium acremonium. The yield of protoplasts, based on DNA content, was up to 18 %. Pretreatment of the mycelium with a thiol compound was necessary with Cephalosporium but not with Penicillium. Electron micrographs indicated that the protoplasts contained all the intracellular organelles of the mycelium and were bounded only by a cytoplasmic membrane. The metabolic activity of the protoplasts, as measured by their respiration, ability to maintain intracellular amino-acid pools, and antibiotic production, was similar to that of control mycelium. l-Valine and l-α-aminoadipic acid, which are precursors of penicillin N and cephalosporin C, were taken up and concentrated by the protoplasts of C. acremonium, although the latter transported l-valine less rapidly than did the corresponding mycelium. Protoplasts of P. chrysogenum took up l-valine but not l-α-aminoadipic acid or its δ-ester. There was little or no transport of the corresponding d-amino acids by protoplasts of either organism.

Isolation of deacetoxycephalosporin C from fermentation broths of Penicillium chrysogenum transformants: construction of a new fungal biosynthetic pathway.

Deacetoxycephalosporin C (DAOC), a precursor of cephalosporins excreted by Cephalosporium and Streptomyces species, has been produced in Penicillium chrysogenum transformed with DNA containing a hybrid penicillin N expandase gene (cefEh) and a hybrid isopenicillin N epimerase gene (cefDh). DAOC from a P. chrysogenum transformant was identified by ultraviolet light (uv), high performance liquid chromatography (HPLC), nuclear magnetic resonance (NMR) and mass spectrum analyses. P. chrysogenum transformed with DNA containing cefEh without cefDh did not produce DAOC. Untransformed P. chrysogenum produced penicillin V (phenoxymethylpenicillin) but not DAOC. Transformants also produced penicillin V but, in general, less than untransformed P. chrysogenum. The cefEh and cefDh genes were constructed by replacing the open reading frame (ORF) of clonedP. chrysogenum pcbC and penDE genes with the ORF of the Streptomyces clavuligerus expandase gene, cefE, and the ORF of the Streptomyces lipmanii epimerase gene, cefD, respectively. Analyses of representative transformants suggested that production of DAOC occurred via cefEh and cefDh genes stably integrated in the P. chrysogenum genome. DNA from untransformed P. chrysogenum did not hybridize to cefE or cefD gene probes.

Transport and Metabolism of Bacilysin and Other Peptides by Suspensions of Staphylococcus aureus

L-Alanyl-L-tyrosine and glycyl-L-phenylalanine labelled with 14C competed with each other and with the dipeptide antibiotic bacilysin for transport into Staphylococcus aureus NCTC 6571 in a medium which did not support growth. They also competed with other dipeptides and several tripeptides. The fast initial transport ofthe two labelled peptides appeared to show Michaelis-Menten kinetics. Neither was transported into a bacilysin-resistant mutant of S. aureus NCTC 6571, although tyrosine was taken up by the mutant as readily as it was by the parent strain. Uptake of alanyltyrosine or glycylphenylalanine was followed by rapid hydrolysis of the peptide and the excretion of tyrosine or phenylalanine. Glycine liberated from glycylphenylalanine was partly degraded and partly incorporated into the bacterial wall. The behaviour of these dipeptides paralleled the inactivation of bacilysin by suspensions of S. aureus and the appearance of its C-terminal amino acid, anticapsin, in the extracellular fluid.

The Synergistic Action of Cephalosporin C and Benzyl-penicillin against a Penicillinase-producing Strain of Staphylococcus aureus

SUMMARY: Cephalosporin C, a hydrophilic, penicillin-like antibiotic which is insensitive to penicillinase, is much less active than benzylpenicillin against the Oxford strain of Staphylococcus aureus but much more active than benzylpenicillin against a penicillinase-producing strain of S. aurcus (D3R). When used together, cephalosporin C and benzylpenicillin act synergistically against S. aureus strain D3R in vitro, pzesumably because cephalosporin C is a competitive inhibitor of penicillinase. When grown under certain conditions in the presence of cephalosporin C. benzyl-penicillin, or bacitracin, the Oxford staphylococcus gives rise during a single culture to a resistant bacterial population consisting largely or partly of Gram-negative bacilli. In the presence of bacitracin a similar change also occurs with S. aureus strain D3R.

Conversion of 17O/18O labelled δ-(L-α-aminoadlpyl)-L-cysteinyl-D-valine to 17O/18O labelled isopenicillin n in a cell-free extract of cephalosporium acremonium. A study by 17O-NMR spectroscopy and mass spectrometry

Abstract δ -(L-α-Amino[1,1,6- 17O/18O-adipyl]-L-cysteinyl-D-valine was converted into isopenicillin N in cell-free extracts of Cepholosporium acremonium with no loss of 17O/18O label as shown by 17O NMR spectroscopy and mass spectrometry. Incubation of unlabelled tripeptide in a cell-free system containing17O/18O enriched water produced isopenicillin N with no incorporation of 17O/18O.

Penicillin biosynthesis: active site mapping with aminoadipoylcysteinylvaline variants

A series of structural variants on the aminoadipoly moiety of the natural precursor of penicillins, δ-(L-α-aminoadipoyl)-L-cysteinyl-D-valine, have been synthesised and their effectiveness as substrates for the enzyme isopenicillin N synthetase has been determined.

The chemistry of new antibiotics.

S INCE THE chemistry of antibiotics of clinical importance was reviewed by Regna [ I] ten years ago, many more substances in this category have been assigned definitive structures. Since this article is concerned mainly with antibiotics which have become of interest to medicine, directly or indirectly, within the last ten years, important substances such as streptomycin and chloramphenicol are not included. However, most of the new substances belong to groups or families of which the first members had been discovered before 1955. The classification of antibiotics may be based on the nature of the microorganisms by which they are produced, on chemical structures which reflect their biogenesis, or on biological activity. The third procedure has been used here in that a division has been made between substances which are of particular interest because of their antibacterial activity, antifungal activity and wider cytotoxic properties, respectively. Within these broad groups, antibiotics which are structurally related have been brought together.

Penicillin biosynthesis. On the stereochemistry of carbon–sulphur bond formation with modified substrates

Enzymatic conversion of the two modified substrates (S-α-amino-δ-adipyl)-S-cysteinyl-(2R,3R)-3-2H-α-aminobutyrate (2c) and (S-α-amino-δ-adipyl)-S-cysteinyl-(2R,3S)-3-2H-α-aminobutyrate (2d) by the enzyme isopenicillin N synthetase gave from both precursors the same penam product, namely (2S)-2-deuterio-norisopenicillin N, indicating that this enzyme is capable of forming carbon–sulphur bonds by retention and also inversion pathways respectively.