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Biomedical subjects

K T Wang

Publications and source records attributed to K T Wang.

At least 37 records · Page 2Linked to original sources
PubMed1995

Sequence comparison and computer modelling of cardiotoxins and cobrotoxin isolated from Taiwan cobra.

Six cardiotoxins and one neurotoxin isolated and purified from the Taiwan cobra venom (Naja naja atra) possess distinct pharmacological and biochemical properties despite the existence of a grossly similar tertiary structure among these toxins, i. e., a core consisting of a series of short loops and four disulfide bridges. A systematic structure comparison of these major toxin isoforms was made by the secondary-structure predictions together with computer model-building based on the primary sequences and the established X-ray and NMR structures of one published cardiotoxin isoform and cobrotoxin. It is of interest to find that some defined and subtle differences can be detected upon the superposition of these three-dimensional polypeptide chains, which may reflect the intrinsic differences in the surface hydrophobicity of cardiotoxins and cobrotoxin as revealed by hydropathy profiles of these toxins in one of three major loops. The differences seem to correlate with different inhibitory activities exhibited by cardiotoxins in contrast to the lack of activity by cobrotoxin on protein kinase C (PKC).

Amino Acid Sequence↗
PubMed1995

Physicochemical properties of alkaline serine proteases in alcohol.

The alkaline proteases subtilisin Carlsberg and alcalase possess substantial enzymatic activity even when dissolved in ethanol. The crude enzymes were purified by gel filtration and the main fractions suspended in ethanol to give a translucent suspension. Both the supernatant and the resuspended precipitate after high-speed centrifugation were found to have enzymatic activities. The solubility of subtilisin Carlsberg in anhydrous ethanol was found to be 45.1 micrograms/ml and that of alcalase was 48.1 micrograms/ml by Coomassie blue dye-binding method using bovine serum albumin as a standard. In the presence of water, the solubility of both enzymes increased with water content. The stability of enzymes incubated in ethanol was assayed by their amidase and transesterase activities using Ala-Ala-Pro-Phe-pNA as substrate in phosphate buffer (pH8.2) and Moz-Leu-OBzl as substrate in anhydrous ethanol, respectively. The soluble enzymes have a half-life of about 36 hr and that of suspended enzymes about 50 hr in the amidase activity assay, whereas the same soluble enzymes have a half-life of about several hours and that of suspended enzymes 1 h by the transesterase activity assay. The stability of both enzymes decreased as water concentration increased. The diastereoselectivity of the enzyme-catalyzed hydrolysis of diastereo pairs of tetrapeptide esters, L-Ala-L-Ala-(D- or L-)Pro-L-Phe-OMe and L-Ala-L-Ala-(D- or L-)Ala-L-Phe-OMe, in phosphate is as high as that of the transesterification of these substrates in ethanol. It is concluded that active sites and selectivity of alkaline serine proteases in anhydrous alcohol are probably very similar to those in aqueous solution in spite of the fact that a lower reactivity is usually associated with the enzymes in nonaqueous solvents.

Amino Acid Sequence↗
PubMed1995

Immunogenicity of mastoparan B, a cationic tetradecapeptide isolated from the hornet (Vespa basalis) venom, and its structural requirements.

Mastoparan B (MP-B) is a cationic tetradecapeptide (LKLKSIVSWAKKVL-CONH2, mol. wt 1611) isolated from the black-bellied hornet (Vespa basalis) venom. The small peptide itself was capable of inducing antibodies without prior conjugation to a protein carrier in rabbits and mice. The mouse antibody was found to be of IgG1 isotype with kappa-type light chain. The peptide antigen was able to form insoluble complexes with the specific antibody, suggesting that MP-B possessed more than one epitope in its molecule. The finding that MP-B was able to bind with both mouse and rabbit antibodies in sandwich ELISA supports this contention. Synthetic MP-B analogues in which lysine at position 2, 4, 11 or 12 was replaced by neutral amino acids such as asparagine or leucine showed a significant decrease in their antibody-binding activities. Substitution of lysine at position 4 (Lys4) caused the most marked inhibition in its binding activity. However, replacing tryptophan at position 9 by tyrosine caused a relatively small reduction in its binding activity. Replacing both Lys2,4 by asparagine or removing Lys-containing segments at amino or carboxyl terminus in MP-B sequence caused a remarkable decrease in the antibody-binding and immunogenic activities of the peptide. The Lys residues located at amino and carboxyl terminal segments of MP-B, especially Lys4, appear to play a critical role in the binding interaction and the immunogenicity of the peptide.

Amino Acid Sequence↗
PubMed1995

Inhibition of protein kinase C by snake venom toxins: comparison of enzyme inhibition, lethality and hemolysis among different cardiotoxin isoforms.

Cardiotoxins, neurotoxins and phospholipase A2 (PLA2) are three major classes of toxic components present in the Taiwan cobra, Naja naja atra of the Elapidae family. Cardiotoxins (or called cytotoxins), a group of major polypeptides of around 60 amino-acid residues present abundantly in the elapid family of snakes, comprise about 45-55% of the crude venom of Taiwan cobra. In contrast to another prominent group of structurally similar neurotoxins with well-established acetylcholine receptors and modes of action, cardiotoxins showed no defined cellular targets and very diverse pharmacological functions. A systematic structure/function comparison of these toxins was made by their relative inhibitory effects on protein kinase C (PKC) isolated from mouse brains. Lethality and hemolysis of various cardiotoxin isoforms were also compared in order to shed some insight on the biological targets and mechanisms of these surface-active amphiphilic polypeptides. A structure comparison of these cardiotoxins based on computer model-building revealed that some defined and subtle differences can be detected upon the superposition of these three-dimensional polypeptide chains, which may reflect the intrinsic differences in the hydrophobic peptide segments present on the surface loops of toxin molecules. The differences seem to correlate with different inhibitory activities exhibited by cardiotoxins in contrast to the lack of activity by cobrotoxin and PLA2 on PKC.

Animals↗
PubMed1995

[Impact of exercise on athlete's cardiac muscle evaluated by Troponin T test].

Twenty-four nursing college students ages 16 to 17 Year were selected as research subjects and divided into two group. Group A comprised 12 individuals who were trained for short distance running (5KM/day) over a five week period, while Group B was trained for middle distance running (7KM/day) during the same period. Breathing frequency, blood pressure, pulse rate and body surface skin temperature were measured at rest (before training) and after exercise every week. Troponin T (TnT). Creatin kinase (CK), Creatine kinase -MB (CK-MB), and Lactate Dehydrogenase (LDH) tests were performed using blood samples and were used as indicators of the impact on heart muscle during exercise. There were no significant differences in breathing frequency, blood pressure, pulse rate or body surface skin temperature between groups A and B before or after training. After one week, the CK levels in both group were higher after exercising than before the training program had begun, and there were significant differences (P < 0.05) between the two groups. Thenceforth, the CK levels in group A decreased to the normal values and stayed the same throughout the fifth week. The CK levels in group B decreased to the normal value after training for three weeks, and there were significant differences between the values before exercising and those for the forth and fifth weeks of training. Although the levels of CK-MB, LDH, and Troponin-T increased after training, all were within the normal range, and no significant difference was observed before or after five weeks of training.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1994

Cardiovascular effects of mastoparan B and its structural requirements.

Mastoparan B is a cationic, amphiphilic tetradecaeptide (LKLKSIVSWAKKVL-CONH2) isolated from the venom of the hornet Vespa basalis. Intravenous injection of the peptide into rats caused a profound depression of blood pressure and cardiac function, which was inhibited by cyproheptadine, reserpine and multiple doses of compound 48/80, but not by diphenhydramine and cromolyn. Mastoparan from Paravespula lewisii showed little cardiovascular inhibitory activity. A synthetic mastoparan B analog in which lysine at position 2 was replaced by asparagine showed a marked decrease in the cardiovascular depressor effects, while replacing lysine at position 4, 11 or 12 with leucine did not cause a significant reduction in these effects. Replacing lysine at position 12 with leucine even caused a more sustained depressor effect. However, the analog in which lysines at positions 11 and 12 were replaced by leucine lost its cardiovascular inhibitory activity. Replacing tryptophan at position 9 with phenylalanine in mastoparan B did not affect its activity. It is concluded that mastoparan B is involved in the cardiovascular disturbances induced by the hornet venom. Lysine at position 2 is a critical residue for the cardiovascular effects of mastoparan B. A peptide molecule with two lysine residues, one located close to the amino terminus and the other near the carboxyl end of the peptide, appears to be the optimal structure for eliciting the cardiovascular depressor effects.

Amino Acid Sequence↗
PubMed1994

D-Aminoacylase from Alcaligenes faecalis possesses novel activities on D-methionine.

D-Aminoacylase isolated from Alcaligenes faecalis DA1 has a great potential for future application in D-amino acids production. This paper reports for the first time that D-aminoacylase can reverse the catalysis direction on D-Met and deacylate N-Ac-D-Met-OMe and N-Ac-D-Met-Gly. The results provide important insights regarding the binding and affinity of substrates to the active site of this enzyme. Based on a systematic study of kinetic properties and relative reactivities for a broad range of substrates, a model to elucidate the reaction mechanism is proposed.

Acylation↗
PubMed1994

Chemical synthesis of gamma-echistatin analogues: elucidation of status of C-terminal (45-49).

Three analogues of gamma-echistatin, des(45-49)-gamma-echistatin, des(46-49)-gamma-echistatin and des(47-49)-gamma-echistatin, were synthesized by solid-phase methodology and their biological activities were measured and compared. The results reveal that without the C-terminal (45-49) of gamma-echistatin, the folding of the protein to the final active structure is not interfered with and Lys-45 influences the inhibition of platelet aggregation.

Amino Acid Sequence↗
PubMed1994

[Physiological changes in the metabolism of football trainees following a match under high temperature].

The effects of a football match on the muscle metabolism of long-term football players were studied. Twenty-two senior high school students (Age: 16.95 +/- 0.82 y/o) were divided into two groups. Group A, included the subjects with longer histories of playing football (7 years) and group B were those with a shorter histories (6 years). There was no statistical difference between the two groups (p > 0.05). The temperature of all muscles tested showed statistical differences after exercise (p < 0.05). After 24 hours, all muscles except the gluteus maximus returned to the normal state while the skin temperature of the latissimus dorsi did not have any change. Body temperature, pulse rate, respiratory rate, and diastolic pressure all significantly increased immediately after the match (p < 0.05) and they all returned to their normal resting rate within one hour, except the body temperature, which required two hours to return to normal. A comparison between groups A and B showed a significant difference (p < 0.01) in creatine kinase level immediately and one hour after the match. It is inferred that energy is derived from the aerobic system.

Adolescent↗
PubMed1993

Investigating the s-2 subsite selectivity of alkaline proteases in hydrolysis of diastereo-peptide esters and molecular-modeling interpretation.

Diastereomeric peptide-esters (Ala-Ala-AA2-Phe-OMe, AA2 = Gly, D- or L-Ala, Pro, Phe, Lys, and Glu) have been used as substrates, and the kinetic constants (Kcat and Km) of the three alkaline proteases, subtilisin Carlsberg, alcalase, and Nagarse (subtilisin BPN') catalyzed ester-hydrolysis, were measured to investigate the selectivity of the enzyme-catalyzed peptide esterhydrolysis. All three proteases preferred the substrate which had a small side-chain at the s-2 site. Thus, the substrates with a bulky side-chain at the p-2 site such as Phe, Pro, Glu, and Lys, hydrolyzed with a rate of about one-tenth that of Ala at the p-2 site, and the Kcat decreased as the size of the p-2 amino acid residue increased. The diastereoselectivity of the alkaline protease-catalyzed hydrolysis of each diastereomeric pair depended on the size of the amino acid residue at the p-2 position of the substrate. The substrates with a bulky side-chain at the p-2 site hydrolyzed with higher diastereoselectivity than did the substrates with a small side-chain at the p-2 site. Molecular modeling of the enzyme-substrate complex show that: for the enzyme complexed with a substrate which has L-L-L-L configuration, each residue of the L-L-L-L tetrapeptide filled in and was completely enclosed by the cleft of the four subsites of the enzyme. The side-chains of the residues were identically positioned within the pocket of the binding-site. For the complex of enzyme with substrate of L-L-D-L, the side-chain of the D-amino acid residue was far away from the s-2 subsite of the enzyme, and had close contact with the side-chains of Leu-126 and Ile-107 of the enzyme.

Amino Acid Sequence↗
PubMed1993

Mastoparan B, synthesis and its physical and biological properties.

Mastoparan B, a tetradecapeptide toxin (LKLKSIVSWAKKVL) isolated from the hornet (Vespa basalis) venom, was synthesized chemically. The physical and biological properties of both the native and synthetic peptides were studied and proved to be identical. Mastoparan B was found to have a potent antibacterial activity to both Gram negative and Gram positive bacteria.

Amino Acid Sequence↗
PubMed1992

Copper transfer and activation of the Streptomyces apotyrosinase are mediated through a complex formation between apotyrosinase and its trans-activator MelC1.

The melanin operon (melC) of Streptomyces antibioticus is composed of two genes that encode MelC1 and MelC2 proteins. MelC1 has been suggested as a trans-activator which can facilitate the incorporation of copper into the apotyrosinase (MelC2) (Lee, Y.-H. W., Chen, B.-F., Wu, S.-Y., Leu, W.-M., Lin, J.-J., Chen, C. W., and Lo, S. J. (1988) Gene (Amst.) 65, 71-81). However, the molecular mechanism of the trans-activation or copper-transfer process mediated through MelC1 to MelC2 is not clear yet. In this study, we found apotyrosinase in both the extracellular fraction and cell extract from cells grown in copper-deficient medium. Using gel-filtration and immunoaffinity chromatographies, we demonstrated that apotyrosinase (MelC2) formed a stable complex with MelC1 in the intra- and extracellular fractions. Furthermore, addition of copper ion to the complex generated tyrosinase activity. The MelC1-MelC2 complex was purified to near homogeneity by DE52 and phenyl-agarose chromatographies. In conjunction with fast protein liquid gel filtration chromatography and NH2-terminal sequencing analysis, the results indicated that the stoichiometric ratio of MelC1 and MelC2 in the purified complex was 1:1. Essentially no copper was found in the complex. Addition of copper ion to the purified complex resulted in incorporation of approximately 2 molecules of copper ion and the mature active tyrosinase was gradually released from the complex. Taken together, these results demonstrate that the molecular mechanism of activation of Streptomyces apotyrosinase by its trans-activator MelC1 is initially mediated via a binary complex formation between these two proteins, followed by incorporation of copper ion. This activation mechanism accounts for the essential role of MelC1 in the expression of melanin operon.

Amino Acid Sequence↗
PubMed1992

Kinetic analysis of duck epsilon-crystallin with L-lactate dehydrogenase activity: determination of kinetic constants and comparison of substrate specificity.

A systematic analysis of the kinetic properties of duck lens epsilon-crystallin with lactate dehydrogenase [LDH, (E.C. 1.1.1.27)] activity was carried out by employing some 19 different alpha-keto acids as substrates for this NADH-dependent LDH-catalyzed reaction. The steady-state Michaelis and catalytic constants (Km, kcat) were determined for a broad range of organic compounds. The results provide important insights regarding the binding and affinity of substrates to active sites of this enzyme crystallin and indicate a great potential for the application of the stable epsilon-crystallin as a catalyst to the synthesis of some important chiral alpha-hydroxyacids in a convenient and efficient way. It is also demonstrated for the first time that in addition to the enzymatic activity of lactate dehydrogenase, duck epsilon-crystallin also possesses the enzymatic activity of malate dehydrogenase.

Animals↗
PubMed1992

Facile synthesis of chiral 2-hydroxy acids catalyzed by a stable duck epsilon-crystallin with endogenous L-lactate dehydrogenase activity.

Duck epsilon-crystallin, an abundant structural protein in lenses of some avian species, was shown to possess a genuine and stable L-lactate dehydrogenase (L-LDH; EC 1.1.1.27) activity suitable for the application to enzyme technology as a catalyst for the synthesis of chiral alpha-hydroxy acids. Two pharmaceutically important intermediates, 2-hydroxy acids (S)-2-hydroxybutanoic acid (S)-2-hydroxypentanoic acid have been synthesized in high yields and optical purity utilizing an in situ NADH regeneration system of duck epsilon-crystallin coupled with formate/formate dehydrogenase. This enzyme system is also shown to offer some advantages over the conventional L-LDH sources from several mammalian species.

Animals↗
PubMed1992

Specific peptide-bond cleavage by microwave irradiation in weak acid solution.

A rapid and selective peptide-bond cleavage in weak acid, induced by microwave irradiation, has been developed. The specific cleavage sites of peptide bonds located only at the carboxyl- and amino-terminal ends of aspartyl residues along the peptide chain. A systematic study including the time course for the cleavage of various aspartyl-containing peptides, the effect of the acidity of the reaction solution on the completeness of peptide-bond cleavage, and the relationship between the power of microwave irradiation and the reaction time of cleavage are studied.

Amino Acid Sequence↗
PubMed1992

[Muscle histochemical changes in rats swimming under high temperature].

The aim of this study was to investigate the effects on muscle tissues of increasing amounts of exercise under normal and high temperatures. An experimental swimming test was applied to completely exercised rats. There were 42 adult male rats divided into 4 groups, including normal control rats, rats which swam to death under room or high temperature conditions, and rats swimming under high temperatures. Immediately after the exercise, the soleus (SOL) and extensor digitorum longus (EDL) muscles were removed by surgical excision. All specimens were frozen in isopentane cooled to -70 degrees C in liquid nitrogen. Cryostat cross sections were cut and stained using histologic and histochemical staining methods to observe pathological changes. The major changes included interstitial edema, muscle fiber atrophy, muscle fiber necrosis, hypercontracted fibers, and ragged red fibers. The rats exercised to death under high temperatures had more apparent changes than those not exercised to death. These results indicate that pathological changes in muscle will be brought about by increasing the amount of exercise and environmental temperature. Since there are more fast twitch fibers in the EDL than in the soleus, pathological changes in muscle tissues are more severe in the EDL.

Animals↗