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Biomedical subjects

K K Han

Publications and source records attributed to K K Han.

At least 19 recordsLinked to original sources
PubMed1992

Characterization of different proteolytic activities in Trypanosoma brucei brucei.

The variant surface glycoprotein of African trypanosomes is released after overnight incubation of parasites at 4 degrees C in pH 5.5 phosphate glucose buffer and may be purified by Concanavalin A Sepharose affinity chromatography. The addition of proteinase inhibitors during the parasite incubation is necessary to prevent the proteolysis of the variant surface glycoprotein by the trypanosomal released proteinases. Using this procedure without the addition of proteinase inhibitors, the proteolytic activities, released from the bloodstream forms Trypanosoma brucei brucei variant AnTat 1.1, were separated by Concanavalin-A Sepharose affinity chromatography. The unretained material (F1) shows hydrolytic activity against the two synthetic substrates Z-Phe-Arg-AMC and Z-Arg-Arg-AMC, which is stimulated by dithiothreitol, but not inhibited by E-64, and characterized by an alkaline pH optimum and an estimated molecular mass of 80-100 kDa. The Michaelis constant for the substrates Z-Arg-Arg-AMC and Z-Phe-Arg-AMC was, respectively, 2.8 and 6.7 microM. The retained material eluted by addition of 1% methyl-alpha-D-mannopyranoside (F2) shows hydrolytic activity against the synthetic substrate Z-Phe-Arg-AMC, which is stimulated by dithiothreitol, inhibited by E-64, active between pH 6.0 and 8.0, and could be separated into two peaks of activity by HPLC, one peak of high molecular mass (greater than 70 kDa) and the other peak of lower molecular mass (30-70 kDa). By electrophoresis in gels containing gelatin as substrate, this fraction contains several proteins with gelatinolytic activity, whereas the unretained fraction F1 did not have any gelatinolytic activity.

Amino Acid Sequence↗
PubMed1992

Possible relationship between coding recognition amino acid sequence motif or residue(s) and post-translational chemical modification of proteins.

1. The "code-sequence" of N-glycosylation site(s), the amino acids located around O-glycosylation site(s), the sequence motifs of several kinases, the sequence motifs of--sulfation, amidation, isoprenylation, myristoylation, palmitoylation and N-acetylation, Aspartic and Asparagine hydroxylation-site, gamma-carboxyglutamate domain, phosphopantetheine attachment site etc. are extensively listed, compared to those reported by "PROSITE" Computer Screen Center and discussed. 2. The structural aspects of protein-DNA recognition are quoted as discussion and conclusion.

Acetylation↗
PubMed1992

Post-translational chemical modification(s) of proteins.

1. The role played by the modification of protein in determining its fate is reported by us. 2. Post-translational modifications such as acetylation, phosphorylation, sulfation, methylation, hydroxylation, ADP-ribosylation, maturation, amidation, carboxylation, adenylylation, glycosylation, ubiquitination, and prenylation are extensively reviewed. 3. Each post-translational modification's significance and its role played in biological function(s) is summarized in the general discussion and the conclusion's remark is directed at the problems left to solve (e.g. post-translational modification reactions in recombinant protein in modern genetic engineering).

Amino Acid Sequence↗
PubMed1992

Estradiol, progesterone and testosterone exposures affect the atrial natriuretic peptide gene expression in vivo in rats.

To clarify the effects of sex hormones on the expression of atrial natriuretic peptide (ANP), ovariectomized and intact female rats were subcutaneously injected with estradiol, progesterone, a mixture of them or olive oil solvent; castrated and untouched male rats were subcutaneously injected with estradiol, testosterone or olive oil, once a day for 7 days. The relative rANP-mRNA contents of rat atrial were measured by molecular hybridization. rANP-cDNA was labeled with 32P as a probe. The results revealed that estradiol and progesterone increased ANP gene expression. Furthermore their effects were associated with administration dose of these hormones and it was shown that they are probably coordinated. The physiological amounts of estradiol and progesterone may maintain suitable levels of rANP-mRNA and androgen may also increase the ANP gene expression in vivo. These experiments suggested that female sex hormone may have a dual purpose in fluid balance.

Animals↗
PubMed1992

The heavy chains of human plasma inter-alpha-trypsin inhibitor: their isolation, their identification by electrophoresis and partial sequencing. Differential reactivity with concanavalin A.

Inter-alpha-trypsin inhibitor (ITI) is a complex protein made up of a light chain so-called bikunin and two heavy chains (apparent Mr values 96000 and 86000 in SDS/PAGE in non-reducing conditions). By sequence analysis, we clearly identified those two components as H1 and H2, respectively. We demonstrate that alkaline treatment (50mM NaOH during 5 min at room temperature) as well as chondroitinase digestion both lead to the dissociation of ITI. The conditions used for alkaline treatment were previously reported for cleavage of the covalent linkage between bikunin and H3 inside pre-alpha-trypsin inhibitor (Enghild et al. (1991) J. Biol. Chem. 266, 747-751). Carbohydrate analysis of the two heavy chains isolated by ion-exchange chromatography suggests the presence of complex-type N-glycans in both H1 and H2 and that of O-glycans in H2. H1 is eluted from Con-A Sepharose by alpha-methylmannoside, in agreement with the existence of at least one biantennary glycan chain. In contrast, H2 remains strongly bound to this support when submitted to the same conditions. Therefore this binding does not depend on carbohydrates. The capacity of H2 to develop such interactions is discussed with regard to the unusual bindings likely to exist between the different peptide chains constituting ITI.

Alpha-Globulins↗
PubMed1992

Selective inhibition of normal murine myelopoiesis "in vitro" by a Hox 2.3 antisense oligodeoxynucleotide.

Multiple homeobox genes are expressed in haematopoietic cell lineages and their expression is cell-type specific. Thus we hypothesized that certain homeobox genes may play an important role in the process of haematopoiesis. To prove that issue, normal murine bone marrow cells were stimulated with appropriate Colony Stimulating Factors in the presence of mouse homeobox gene (Hox 2.3) sense or antisense oligodeoxynucleotides and the effects on the haematopoietic colony formation were examined. Treatment of the cells to Hox 2.3 antisense oligodeoxynucleotides led to a selective inhibition of myeloid colony formation, both in size and in numbers, but without significant effect on erythroid and megakaryocytic haematopoiesis. Exposure to Hox 2.3 sense oligodeoxynucleotides (no-oligomers), had no such effect. It was further showed that inhibition of myelopoiesis by Hox 2.3 antisense oligodeoxynucleotides was dependent on the differentiation stage of target cells. These findings demonstrated that Hox 2.3 gene plays a critical role in regulating normal murine myelopoiesis.

Animals↗
PubMed1991

The effects of streptozotocin induced diabetes mellitus and fish oil compound on gene expression of atrial natriuretic peptide in rat.

1. Adult male Wistar rats were injected with streptozotocin (STZ: 55 mg/kg) for inducing diabetes. Then blood and atria for RNA extraction were withdrawn from rats treated 3 and 11 weeks previously with STZ respectively. Atrial total RNA were extracted with cold phenol method. The ANP mRNA contents were determined using Dot blot hybridization technique with alpha-32-P-labelled r-prepro ANP cDNA probe. 2. Plasma glucose was increased and plasma immunoreactive insulin was lowered in rats at 3 and 11 weeks after injection of STZ. ANP gene expression in diabetic rats was depressed. ANP mRNA contents in rats treated 3 and 11 weeks with STZ were 86.4% and 31.7% of that of control rats. 3. Three weeks after treatment of STZ, the rats were gastrically perfused with FOC (Fish Oil Compound) (0.355 ml/kg) once a day successively until 11 weeks. This treatment induces lower blood pressure in rats. ANP gene expression in FOC group was apparently recovered which had been decreased because of the effect of diabetes mellitus.

Animals↗
PubMed1990

The effects of salt-loading and dehydration on atrial natriuretic peptide (ANP) gene expression.

1. Effects of sodium loading and dehydration on ANP gene expression were investigated in rats. 2. ANP-mRNA was determined using Northern blot and dot blot hybridization technique with alpha-32P-labeled r-preproANP-cDNA probe. Salt loading increased the ANP-mRNA content in atria. Correlation with ANP-mRNA content and the plasma sodium concentration was established. 3. Deprivation of water for 2 and 4 days increased ANP-mRNA 2.1- and 1.6-fold, respectively. 4. These results demonstrated that water-salt balance affects the ANP-gene expression.

Animals↗
PubMed1979

[Quantitative determination of the activity of acid peptidases of industrial origin].

Reagent ninhydrine-Cd++, reacts with free alpha and epsilon amino groups of proteins. Horse-heart apomyoglobin was subjected to exhaustive succinylation, rendering the product non reactive to ninhydrine. The succinylglobin was submitted to enzyme digestion at pH 2.0, 4.0, 4.7 and 6.0. The commercially available enzymes contain mainly pepsin-like and chymosin-like enzymes. The enzymatic digests of succinyl-globin contain new free alpha-amino groups reacting with ninhydrin. Enzymatic digestion was performed under various condition (ratio E/S, pH). The results were compared to those obtained with synthetic substrate: PRO-HIS-LEU-SER-PHE(NO2)-NLEU-ALA-LEU-OME. The price of the synthetic substrate used, was more than 100 times the cost of succinyl-globin, thus the use of this substrate is a valuable tool for the quantitative estimation of peptidase activity in commercially available (pepsin, chymosin-like) enzymes.

Apoproteins↗
PubMed1979

Evidence for the resistance of thyrotropin-releasing hormone (TRH) and pseudo-hormone, pyroglutamyl histidyl-amphetamine, to degradation by enzymes of the digestive tract in vitro.

TRH and pseudo-hormone (pyro Glu-His-amphetamine) were submitted to the digestion of chymotrypsin and prolidase and independently to the digestion of enzymes of the digestive track: pepsin (stomach), pancreatins (pancreas) and enzymes extracted from the intestinal mucosa (small intestine). Using thin layer chromatography and high voltage electrophoresis techniques to detect enzymic digestion products, only intact TRH and pseudo-hormone were found, indicating that both entities were, under the conditions used, resistant to in vitro digestion by enzymes of the digestive tract.

Amphetamines↗
PubMed1979

Isolation and characterization of desmosine(s) containing peptide fractions of normal and diseases human aortic elastin.

Normal and diseased human aortic elastins were isolated and highly purified. They were subsequently submitted to elastase and thermolysin digestion followed by partial acid hydrolysis to increase crosslinkage. The peptide fractions containing these highly cross-linked desmosines were extensively purified either by ion exchange chromatography or by gel-filtration. Their amino acid composition was determined. Detailed investigation of the purified peptide fraction from normal human elastin containing desmosines was carried out using different N-terminal and C-terminal procedures, thus permitting the probable covalent structure of the desmosine containing peptide(s) to be proposed. Irrespective of their origin (healthy or pathologic), the elastin samples all revealed the same amino acid composition with a very high alanine content in the cross-linking peptides. This work is submitted as proof that changes in amino acid composition are essentially due to "dilution" and contamination by structural glycoproteins and not to structural changes in amino acid compoistion in the vicinal cross-links positions. We find that not only "clustering" alanine residues but also glycine, proline, valine, leucine and tyrosine residues are located in the immediate vicinity of both desmosine and isodesmosine residues.

Amino Acid Sequence↗
PubMed1978

The amino acid sequence of the alpha chain of badger (Meles meles) haemoglobin.

The complete amino acid sequence of the alpha chain from the badger (Meles meles) haemoglobin was elucidated using conventional methods chiefly performed on tryptic peptides separated by peptide "mapping" and comparison with human alpha chain. Sixteen differences were noted between the alpha chain of badger and man. Phylogenetic aspects and three-dimensional structure requirements are discussed.

Amino Acid Sequence↗