Showing papers on "Ribostamycin published in 1990"

Comparative ototoxicity of ribostamycin, dactimicin, dibekacin, kanamycin, amikacin, tobramycin, gentamicin, sisomicin and netilmicin in the inner ear of guinea pigs.

Abstract: Nine aminoglycoside antibiotics, ribostamycin (RSM), dactimicin (DAC), dibekacin (DKB), kanamycin (KM), amikacin (AMK), netilmicin (NTL), tobramycin (TOB), gentamicin (GM) and sisomicin (SISO) were ad

Aminoglycoside blockade of Ca2(+)-activated K+ channel from rat brain synaptosomal membranes incorporated into planar bilayers.

Abstract: Ca2(+)-activated K+ channels from rat brain synaptosomal membranes were incorporated into planar lipid bilayers, and the effects of aminoglycoside antibiotics on the single channel conductance (258 +/- 13 pS at 100 mM K+) were investigated. Aminoglycosides reduced the single channel conductance from the 'cis' (cytoplasmic) side in a dose- and voltage-dependent manner. Voltage dependence of the blockade indicated an interaction between positively charged amino residues of aminoglycoside antibiotics and a binding site located within the electric field of the ion-conducting pathway. The order of blocking potency was consistent with that of the number of amino residues of aminoglycosides (neomycin (6) greater than dibekacin (5) greater than ribostamycin (4) = kanamycin (4], while the electrical distance (z delta = 0.46-0.49) of the binding site kept almost constant for each drug. These z delta s were almost the same with those (0.46-0.51) of alkyl-diamine blockers with two amino residues (total net charge of +2) and approximately twice of those (0.25-0.26) of alkylmonoamine blockers (total net charge of +1). Assuming that amino residues of aminoglycosides and alkylamines shared the same binding site located at 25% voltage drop from the cytoplasmic surface of the channel, the site would have to be at least large enough to accommodate one diamino sugar residue of the aminoglycoside in order to simultaneously interact with two positively charged amino groups. Dose- and voltage-dependent blockade of the channel by gallamine, an extremely bulky trivalent organic cation, supported the picture that the channel has a wide mouth on the cytoplasmic side and its 'pore' region, where voltage drop occurs, may also be quite wide and nonselective, suddenly tapering to a constriction where most charged cations block the channel by 'occluding' the K(+)-conducting pathway.

Cloning of aminoglycoside phosphotransferase (APH) gene from antibiotic-producing strain of Bacillus circulans into a high-expression vector, pKK223-3. Purification, properties and location of the enzyme.

Abstract: The aminoglycoside phosphotransferase gene from a butirosin-producing strain of Bacillus circulans was cloned in a high-expression vector (pKK223-3) to give the recombinant plasmid pMS5. Escherichia coli harbouring the plasmid, E. coli JM103[pMS5], was characterized, and several features of the expression of the phosphotransferase were studied. The phosphotransferase activity was best expressed in a medium lacking glucose, and the highest levels of the enzyme were found between 12 and 24 h of growth. The induction of the phosphotransferase expression with isopropyl beta-D-thiogalactopyranoside (inducer) was found to be undesirable as the overproduction of the enzyme led to the killing of the bacteria. The subcellular location of the phosphotransferase, and also the site in vivo of the phosphorylation of neomycin, was found to be in the cytoplasm. The phosphotransferase was purified to homogeneity in good yield (17 mg of purified protein/3 litres of culture) and was shown to be a monomer of Mr 30,000-32,000. The N-terminal amino acid sequence was in agreement with that predicted from the gene sequence and confirmed the absence of any signal sequence. The regiospecificity of the phosphotransferase reaction was studied by m.s. and by 1H-, 13C- and 31P-n.m.r. using ribostamycin as the substrate, and it was found that the antibiotic was phosphorylated at the 3'-hydroxy group.

Preparation of aminoglycosides

Abstract: N-Substituted derivatives of aminoglycosides are prepared by (a) complexing an aminoglycoside with divalent metal ion selected from the group consisting of the cations of Fe, CO, Ni, Cu, Pd, Ag and Pt to form a protected species having at least one amino group bound as a metal ion chelate and at least one unbound amino group, (b) reacting the protected species with an N-acylating reagent selected from the group consisting of carboxylic and sulfonic acid anhydrides, halides and active esters to acylate at least one unbound amino group, and (c) removing the amino-protecting chelate groups Among the aminoglycosides useful are kanamycin A, kanamycin B, kanamycin C, sisomicin, gentamicin B, tobramycin, ribostamycin, butirosin A, butirosin B, neomycin B, paromomycin I, lividomycin A and lividomycin B The N-substituted derivatives possess utility as antibiotics or as intermediates in the preparation of aminoglycoside antibiotics

Purification and Characterisation of Gentamicin Acetyl Transferase

Abstract: Homogeneous gentamicin acetyl transferase from Escherichia coli JR225 was isolated using four major steps: ion-exchange chromatography on DEAE-Sepharose, dye ligand chromatography on Procion Scarlet H-2G Sepharose, ion exchange by FPLC MonoQ HR 10/10 and gel-filtration by FPLC Superose 12 10/30. The purified enzyme had a specific activity of approximately 34 units/mg of protein and was shown to exist as a dimer of subunit molecular weight 30,000. The isoelectric point of the enzyme was calculated to be 5.34. The enzyme was maximally active at pH8.5 and at a temperature of 50°C. The enzyme shows Michaelis-Menten kinetics with Km values of: gentamicin (µM) apramycin (83µM), kanamycin (202µM), neomycin (31µM), netilmicin (2µM), ribostamycin (190µM)soframycin (21µM).The enzyme shows some activity towards 2-deoxystreptamine.