Studies on rat mammary gland acetyl-CoA carboxylase.
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Acetyl-CoA Carboxylase↗
Biomedical subjects
F Ahmad
Publications and source records attributed to F Ahmad.
Thermodynamic characterization of the partially denatured states of ribonuclease A in calcium chloride and lithium chloride.
The denaturations of ribonuclease A by calcium chloride and lithium chloride were studied by circular dichroism measurements in the far-ultraviolet region. The temperature dependence of the equilibrium constant for the unfolding of the protein by calcium chloride and lithium chloride gave values of 46 and 52 kcal mol-1 (1 cal = 4.1868 J) for the enthalpy of denaturation at 25 degrees C and pH 7.0, respectively. Thermodynamic parameters for the denaturation by calcium chloride and lithium chloride are compared with those for the heat and guanidine hydrochloride denaturation. It has been observed that the thermodynamic quantity, be it free energy, entropy, or enthalpy, cannot be related quantitatively to the extent of unfolding measured by various conformational properties of the protein.
Animals↗
Infection and Branhamella catarrhalis.
Of the Gram-negative cocci found in the nasopharynx to which any pathogenic status can be attributed, Neisseria meningitidis and Neisseria (Branhamella) catarrhalis have gained significant notoriety. Traditionally, B. catarrhalis is regarded as a nasopharyngeal commensal and thus there is, in general, considerable reluctance to accept that B. catarrhalis may be a pathogen when it is seen. Hence, it is under-reported or totally ignored though there is more awareness regarding its pathogenic potential, particularly as an increasingly high incidence of beta lactamase producing strains is being reported from many countries. The importance of this development concerns the choice of routine antibiotic therapy as ampicillin, to which this organism was previously sensitive, may no longer be effective.
Conjunctivitis↗
A survey of the neoplastic lesions in the north western region of Pakistan.
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Adolescent↗
Branhamella catarrhalis (beta lactamase positive) ophthalmia neonatorum.
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Female↗
Inhibitory effects of sulfhydryl reagents on acetyl-CoA carboxylase from rat mammary gland.
Rat mammary gland acetyl-CoA carboxylase (acetyl-CoA:carbon dioxide ligase (ADP forming), EC 6.4.1.2) is rapidly and irreversibly inactivated by micromolar concentrations of S-(4-bromo-2,3-dioxobutyl)-CoA (BDB-CoA) or p-hydroxymercuribenzoate (PHMB). Inhibition of both half reactions (i.e., the biotin carboxylation and the carboxyltransferase) catalyzed by acetyl-CoA carboxylase closely parallels loss in overall activity (malonyl-CoA synthesis). The presence of a substrate or product (acetyl-CoA, ATP, ADP, Pi) or inhibitor (palmitoyl-CoA) does not protect the enzyme from inhibition caused by BDB-CoA or PHMB. On the other hand, citrate, an activator of acetyl-CoA carboxylase, affords substantial protection against inhibition by BDB-CoA and PHMB. Covalent modification by BDB-CoA or PHMB appears to lock acetyl-CoA carboxylase in an inactive conformation (15-30 S) that is unable to undergo citrate-induced self-association into the catalytically competent polymeric form.
Acetyl Coenzyme A↗
Free energy changes in denaturation of ribonuclease A by mixed denaturants. Effects of combinations of guanidine hydrochloride and one of the denaturants lithium bromide, lithium chloride, and sodium bromide.
The denaturation of ribonuclease A by guanidine hydrochloride, lithium bromide, and lithium chloride and by mixed denaturants consisting of guanidine hydrochloride and one of the denaturants lithium chloride, lithium bromide, and sodium bromide was followed by difference spectral measurements at pH 4.8 and 25 degrees C. Both components of mixed denaturant systems enhance each other's effect in unfolding the protein. The effect of lithium bromide on the midpoint of guanidine hydrochloride denaturation transition is approximately the sum of the effects of the constituent ions. For all the mixed denaturants tested, the dependence of the free energy change on denaturation is linear. The conformational free energy associated with the guanidine hydrochloride denaturation transition in water is 7.5 +/- 0.1 kcal mol-1, and it is unchanged in the presence of low concentrations of lithium bromide, lithium chloride, and sodium bromide which by themselves are not concentrated enough to unfold the protein. The conformational free energy associated with the lithium bromide denaturation transition in water is 11.7 +/- 0.3 kcal mol-1, and it is not affected by the presence of low concentrations of guanidine hydrochloride which by themselves do not disrupt the structure of native ribonuclease A.
Animals↗
Calcium- and cyclic AMP-regulated protein kinases of bovine central-nervous-system myelin.
Bovine central-nervous-system myelin was found to contain both Ca2+-activated and cyclic AMP-dependent protein kinases. Each enzyme possesses unique solubility and substrate-specificity characteristics. The Ca2+-activated enzyme, like its substrate (basic protein), is probably deeply embedded in the neural membrane, whereas the cyclic AMP-dependent kinase appears to be much less tightly associated with myelin. Treatment of insoluble myelin fraction housing the Ca2+-activated kinase with phospholipase A2 and phospholipases A2 + C causes a decrease in its ability to become activated by Ca2+. This can be countered by phosphatidylserine and phosphatidylethanolamine. Whereas the activity of the Ca2+-activated membrane-associated kinase is inhibited by chlorpromazine, dibucaine, melittin and Triton X-100, it is activated by certain phorbol diesters (4 beta-phorbol 12-myristate 13-acetate, 4 beta-phorbol 12,13-didecanoate, 4 beta-phorbol 12,13-dibenzoate and 4 beta-phorbol 12,13-diacetate), which appear to exert this effect by lowering the concentration of Ca2+ normally required for the activation of this enzyme. Together these results suggest that the activation of the membrane-associated kinase by Ca2+ most probably requires certain lipids, perhaps those already present in the membrane.
Animals↗
Protein synthesis in rabbit reticulocytes: a study of the mechanism of action of the protein factor RF that reverses protein synthesis inhibition in heme-deficient reticulocyte lysates.
A eukaryotic initiation factor 2 (eIF-2)-ancillary protein factor Co-eIF-2 promotes displacement of GDP from eIF-2 X GDP and facilitates ternary complex (Met-tRNAf X eIF-2 X GTP) formation in the presence of Mg2+. Heme-regulated protein synthesis inhibitor, HRI, phosphorylates the alpha-subunit of eIF-2 and thus inhibits ternary complex formation as Co-eIF-2 does not displace GDP from eIF-2 alpha (P) X GDP. RF, a high molecular weight cell supernatant factor, reverses protein synthesis inhibition in heme-deficient reticulocyte lysates and also reverses HRI inhibition of ternary complex formation. RF contains Co-eIF-2 activity. In addition, an active RF preparation contains excess alpha-subunit of eIF-2 in the free and unphosphorylated form and this alpha-subunit of eIF-2 is not phosphorylated by HRI and ATP. In this paper we report (i) an active RF preparation contains excess alpha-subunit of eIF-2 and this alpha-subunit can be phosphorylated by HRI and ATP in the presence of GDP; (ii) RF promotes ternary complex formation by eIF-2 X [3H]GDP with accompanying GDP displacement; (iii) in the presence of HRI and ATP, RF promotes ternary complex formation by eIF-2 X [3H]GDP without accompanying GDP displacement; (iv) in the presence of HRI and ATP, the ternary complex formed using RF is active in Met-tRNAf X 40S initiation complex formation; (v) both the ternary complex and the Met-tRNAf X 40S complex formation in the presence of HRI and ATP are completely inhibited by prior incubation of RF with GDP; (vi) upon further fractionation of an active RF fraction, a preparation can be obtained that contains HRI-sensitive Co-eIF-2 activity. However, this preparation does not efficiently reverse protein synthesis inhibition in heme-deficient reticulocyte lysates and does not contain excess alpha-subunit of eIF-2. Based on these observations, we have suggested (a) RF provides the unphosphorylated alpha-subunit to eIF-2 alpha (P) X GDP and restores eIF-2 activity. This RF activity is inhibited as the alpha-subunit in the RF preparation becomes phosphorylated by HRI and ATP in the presence of GDP; (b) RF contains Co-eIF-2 activity, which has dual functions: (i) stimulation of ternary complex formation by eIF-2 and (ii) GDP displacement from eIF-2 X GDP during ternary complex formation. In the presence of HRI and ATP, Co-eIF-2 but does not displace GDP from eIF-2 alpha(P) X GDP.
Adenosine Triphosphate↗
Antimicrobial susceptibility of Branhamella catarrhalis isolates from bronchopulmonary infections.
Fifty-four clinical isolates of Branhamella catarrhalis from patients with bronchopulmonary infections were studied. The MICs for 50 and 90% of the isolates and the geometric mean MICs were determined for 11 antimicrobial agents. All the strains were resistant to trimethoprim but were susceptible to clavulanate-potentiated amoxicillin (Augmentin; Beecham Research Laboratories, London), chloramphenicol, co-trimoxazole, erythromycin, cefotaxime, and cefuroxime. Beta-lactamase-negative strains were uniformly susceptible to penicillin and ampicillin.
Anti-Bacterial Agents↗
Isolation of Bordetella pertussis: benefits of using both Bordet-Gengou and charcoal agar media.
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Agar↗
Bronchopulmonary infection due to Branhamella catarrhalis.
Over six months Branhamella catarrhalis was isolated in pure culture from the sputum of 81 patients with symptoms of acute respiratory tract infection. Of 38 patients who were infected in the community, over half required admission to hospital. The remaining 43 patients acquired the infection in hospital. Forty one of the 81 isolates produced beta-lactamase, 24 of these being hospital acquired infections. As a result 40% of patients who were treated with ampicillin did not respond. Most patients had chronic lung diseases or lung cancer or were taking corticosteroids. Three patients died and one required assisted ventilation; strains producing beta-lactamase were isolated in each case. Acute bronchitis developed in one previously healthy young non-smoker. It is concluded that B catarrhalis is an important pathogen of the lower respiratory tract which should be reported, and strains producing beta-lactamase should be identified. Otherwise, treatment with inappropriate antibiotics may result in increased morbidity or mortality.
Adult↗
Free energy changes in ribonuclease A denaturation. Effect of urea, guanidine hydrochloride, and lithium salts.
The unfolding of ribonuclease A by urea, guanidine hydrochloride, lithium perchlorate, lithium chloride, and lithium bromide has been followed by circular dichroic and difference spectral measurements. All three abnormal tyrosyl residues are normalized in urea and guanidine hydrochloride (delta epsilon 287 = -2700), only two are normalized in lithium bromide and lithium perchlorate (delta epsilon 287 = -1700), and only one is exposed in lithium chloride solutions (delta epsilon 287 = -700). The Gibbs energies are 4.7 +/- 0.1 kcal mol-1 for urea- and guanidine hydrochloride-denaturation, 3.8 +/- 0.2 kcal mol-1 for lithium perchlorate-denaturation, and 12.7 +/- 0.2 kcal mol-1 for lithium chloride- and lithium bromide-denaturation of ribonuclease A. The latter results suggest that the mechanism of the unfolding process in urea and guanidine hydrochloride is quite different from that in lithium salts.
Animals↗
Free energy changes in lysozyme denaturation.
Previous work has shown that native lysozyme (N) is completely denatured by the addition of guanidinium chloride (conformation D) but that partially denatured conformations appear in other denaturants. Conformation I appears when LiClO4 is added to the protein, and conformation II is caused by heating. We have now determined the apparent free energy changes for the reversible processes between N and the three unfolded conformations and for the process between II and D. This allows us to estimate the apparent free energy changes for a process between any two of these four conformations.
Animals↗
Partial characterization of the phosphotransferase system of human central-nervous-system myelin.
The phosphotransferase system of human central-nervous-system myelin was investigated. Evidence obtained indicated the presence of at least two different phosphotransferase systems (cyclic nucleotide-dependent and -independent) in myelin, which were found to be firmly associated with the membrane. The cyclic AMP-dependent kinase of myelin and white-matter cytosol preferentially phosphorylated certain histone fractions and displayed only modest activity with basic protein as substrate. On the other hand, the cyclic nucleotide-independent system showed specificity toward basic protein. Its activity was not only dependent on Mg2+ but it was greatly enhanced by this bivalent cation. Whereas the cyclic nucleotide-dependent kinase could be extracted with buffers containing Triton X-100, the bivalent cation-regulated kinase resisted solubilization from myelin under these conditions.
Brain↗
Effect of citrate on the different reactions catalyzed by rat mammary gland acetyl CoA carboxylase.
The effect of citrate on the different reactions catalyzed by rat mammary gland acetyl CoA carboxylase has been investigated. Citrate showed modest effect on the ATP-orthophosphate and ATP-ADP exchange reactions. In contrast, this tricarboxylic acid caused marked concentration-dependent stimulation of the acetyl CoA-malonyl CoA exchange reaction which was concomitant with the activation of acetyl CoA carboxylation. The data obtained are consistent with the suggestion that activation by citrate of the overall forward reaction (malonyl CoA synthesis) primarily reflects enhancement of the carboxyltransferase half-reaction catalyzed by rat mammary gland acetyl CoA carboxylase.
Acetyl-CoA Carboxylase↗
Brotizolam as a pre-operative hypnotic.
Efficacy of and tolerance to brotizolam when used as a preoperative hypnotic were studied in two double-blind, randomised parallel group studies. Brotizolam (0.25 and 0.50 mg) was superior to placebo. Efficacy was assessed as good-to-satisfactory in 73.0% of patients with 0.25 mg and in 88.0% with 0.5 mg. A similar assessment was reached in 40.0% of patients with placebo. Brotizolam 0.5 mg was superior to 0.25 mg, and with the higher dose subjective assessments of anxiety were reduced. Efficacy of tolerance to 0.5 mg brotizolam and 2.0 mg flunitrazepam were compared, and both drugs were found to be effective and well tolerated. Brotizolam maintained sleep throughout the night more effectively than flunitrazepam. A dose range of 0.25-0.5 mg brotizolam is recommended as a pre-operative hypnotic.
Adolescent↗
Studies on acetyl-CoA carboxylase and fatty acid synthase from rat mammary gland and mammary tumours.
The activities of two lipogenic enzymes, acetyl-CoA carboxylase and fatty acid synthase, were determined in two transplantable mammary adenocarcinomas (13762 and R3230AC) carried by non-pregnant, pregnant and lactating rats, and in mammary tissue of control animals (non-tumour-carrying) of comparable physiological states. During mammary-gland differentiation of control or tumour-carrying animals, the activities of acetyl-CoA carboxylase and fatty acid synthase in the lactating gland increased by about 40--50-fold over the values found in non-pregnant animals. On the other hand, in tumours carried by lactating dams there were only modest increases (1.5--2-fold) in acetyl-CoA carboxylase and fatty acid synthase compared with the neoplasms carried by non-pregnant animals. On the basis of the Km values for different substrates and immunodiffusion and immunotitration data, the fatty acid synthase of neoplastic tissues appeared to be indistinguishable from the control mammary-gland enzyme. However, a comparison of the immunotitration and immunodiffusion experiments indicated that the mammary-gland acetyl-CoA carboxylase might differ from the enzyme present in mammary neoplasms.
Acetyl-CoA Carboxylase↗