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K Moon

Publications and source records attributed to K Moon.

30 records · Page 2Linked to original sources
PubMed1994

Generation and Characterization of Environmentally Sensitive Variants of the beta-Galactosidase from Lactobacillus delbrueckii subsp. bulgaricus.

A method is described for generating and screening variants of the beta-galactosidase from Lactobacillus delbrueckii subsp. bulgaricus sensitive to several environmental stresses, with potential application in the food industry. Chemical mutagenesis with hydroxylamine or methoxylamine was performed on the beta-galactosidase gene carried on an Escherichia coli expression vector. Mutants sensitive to cold, heat, low pH, low magnesium concentration, and the presence of urea were isolated by screening for reduced color development on beta-galactosidase indicator plates. The mutations responsible for three variant beta-galactosidases were localized, and the base substitutions were determined by DNA sequencing. The amino acid alterations associated with one low-pH-sensitive (pHs) and two urea-sensitive (Us) variants correspond to P584L (pHs1), G400S/R479Q (Us26), and G167E/E168K/E363K/V492M (Us17), respectively. Mutant pHs1 is also heat, cold, low magnesium, and urea sensitive; Us26 is also cold sensitive; and Us17 is also low-pH sensitive.

Journal Article↗
PubMed1993

Isolation and characterization of cDNAs encoding wheat 3-hydroxy-3-methylglutaryl coenzyme A reductase.

The enzyme 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMGR, EC 1.1.1.34) is a key enzyme in the isoprenoid biosynthetic pathway. We have isolated partial cDNAs from wheat (Triticum aestivum) using the polymerase chain reaction. Comparison of deduced amino acid sequences of these cDNAs shows that they represent a small family of genes that share a high degree of sequence homology among themselves as well as among genes from other organisms including tomato, Arabidopsis, hamster, human, Drosophila, and yeast. Southern blot analysis reveals the presence of at least four genes. Our results concerning the tissue-specific expression as well as developmental regulation of these HMGR cDNAs highlight the important role of this enzyme in the growth and development of wheat.

Amino Acid Sequence↗
PubMed1991

[A case of EEC (ectrodactyly, ectodermal dysplasia, and cleft lip) syndrome].

EEC syndrome is a rare congenital malformation characterized by ectrodactyly, ectodermal dysplasia, cleft lip and/or palate. We reported a case of EEC syndrome with cleft palate. The patient was a 15-month-old girl. She had split hands of the upper extremities, syndactyly and polydactyly of the right lower extremity, ectodermal dysplasia including sparse hair, enamel hypoplasia and cleft palate. The patient underwent palatoplasty at the age of 18 months.

Abnormalities, Multiple↗
PubMed1986

Nuclear magnetic resonance imaging and spectroscopy in experimental brain edema in a rat model.

Many aspects of the use of high-resolution nuclear magnetic resonance (NMR) imaging in the examination of brain edema have not been fully explored. These include the quantitation of edema fluid, the ability to distinguish between various types of edema, and the extent to which tissue changes other than a change in water content can affect NMR relaxation times. The authors have compared NMR relaxation times obtained by both in vivo magnetic resonance imaging (MRI) and in vitro NMR spectroscopy of brain-tissue samples from young adult rats with cold lesions, fluid-percussion injury, hypoxic-ischemic injury, bacterial cerebritis, and cerebral tumor. Changes in relaxation times were compared with changes in brain water content, cerebral blood volume, and the results of histological examination. In general, both in vivo and in vitro longitudinal relaxation times (T1) and transverse relaxation times (T2) were prolonged in the injured hemispheres of all experimental groups. Water content of tissue from the injured hemispheres was increased in all groups. A linear correlation between T2 (but not T1) and water content was found. Changes in the values of T1 and T2 could be used to distinguish tumor from cold-injured tissue. Cerebral blood volume was reduced in the injured hemispheres and correlated inversely with prolongation of T1 and T2. The results of this study suggest that, in a clinical setting, prolongation of T2 is a better indicator of increased water content than prolongation of T1, yet quantitation of cerebral edema based solely upon prolongation of in vivo or in vitro T1 and T2 should be undertaken with caution.

Animals↗
PubMed1985

Gallbladder bile: an experimental study in dogs using MR imaging and proton MR spectroscopy.

Magnetic resonance (MR) imaging, proton MR spectroscopy, and biochemical analysis were performed to investigate MR signal intensity (SI) differences between concentrated and dilute gallbladder bile of seven fasting and five sincalide-treated dogs. MR images revealed high SI from bile of fasting dogs and low to medium SI in sincalide-treated dogs when spin-echo (SE) pulse sequences with repetition rates of 0.5 and 2.0 sec were used. Proton MR spectra were similar for fasting and sincalide-treated dogs. In fasting dogs, water content in the bile was slightly lower, and cholesterol, phospholipid, and bile acid concentrations were higher. More than 90% of proton signals in all Fourier transform free induction decay spectra emanated from water molecules, and no lipid proton resonances were detected in Fourier transform SE spectra after tau delays of 7 msec. These results indicate that the differences in SI are caused by alterations in relaxation times of water protons, possibly resulting from the interactions of water protons and macromolecules.

Animals↗
PubMed1975

Nicotinamide adenine dinucleotide phosphate-specific glutamate dehydrogenase of Neurospora.

Neurospora NADP-specific glutamate dehydrogenase that was treated with iodoacetate, iodoacetamide, or N-ethylmaleimide to block the thiol groups was cleaved with cyanogen bromide. Of the expected 10 peptides, based on a methionine content of 9 residues, 8 were obtained in pure form and 2 were handled as a mixture. The fragments ranged in size from 9 to 109 residues. In addition, there were isolated 6 peptides, produced by anomalous cleavage at the carboxyl groups of tryptophan residues, and two by hydrolysis of an aspartyl-proline bond. Preliminary separation of these peptides was accomplished by gel filtration followed by either ion-exchange chromatography of the larger peptides or by paper chromatography and paper electrophoresis of the smaller fragments. Ordering of the CNBr fragments in sequence was based upon sequences of tryptic and chymotryptic peptides obtained in another laboratory. The complete sequence of the protein is presented. The amino acid sequences of the bovine and chicken liver glutamate dehydrogenases previously determined show considerable homology with the NADP-specific enzyme of Neurospora in the NH2-terminal half of the molecule; this includes the region of the specifically reactive lysine residue and the portion of the sequence that has been implicated in coenzyme binding. Particularly striking is the fact that most of the residues conserved among the three homologous proteins would be expected to be important for conformational, rather than catalytic, effects. This implies that the conformation of the Neurospora enzyme must be similar in parts of its structure to the vertebrate enzymes but undoubtedly differs in some regards.

Amino Acid Sequence↗
PubMed1974

Amino-acid sequence of NADP-specific glutamate dehydrogenase of neurospora crassa.

A tentative primary structure of the NADP-specific glutamate dehydrogenase [L-glutamate: NADP oxidoreductase (deaminating), EC 1.4.1.4] from Neurospora crassa has been determined. The proposed sequence contains 452 amino-acid residues in each of the identical subunits of the hexameric enzyme. Comparison of the sequence with that of the bovine liver enzyme reveals considerable homology in the amino-terminal portion of the chain, including the vicinity of the reactive lysine, with only shorter stretches of homology within the carboxyl-terminal regions. The significance of this distribution of homologous regions is discussed.

Amino Acid Sequence↗
PubMed1972

Glutamate dehydrogenase: amino-acid sequence of the bovine enzyme and comparison with that from chicken liver.

Further investigation of the amino-acid sequence of bovine glutamate dehydrogenase (EC 1.4.1.3) has led to the correction of an earlier tentative sequence. The presently known sequence contains 500 residues in the subunit single peptide chain. The sequence of the homologous enzyme from chicken liver indicates that it contains 503 residues. Of the presently established 485 residues in the chicken dehydrogenase, only 26 residues differ from those in the bovine enzyme. The chicken dehydrogenase also differs in having an additional three residues at the amino terminus. The amino-terminal residue of the chicken enzyme was found to be cysteic acid.

Amino Acid Sequence↗