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Biomedical subjects

T H Chou

Publications and source records attributed to T H Chou.

34 records · Page 2Linked to original sources
PubMed1980

Electrofocusing patterns of fucosyltransferase activity in plasma of patients with chronic granulocytic leukemia.

Fucosyltransferase activity was measured in plasma samples obtained from patients with chronic granulocytic leukemia in different disease stages. Total enzyme activity was generally elevated in untreated and in stable disease; a marked further elevation was noted 30 to 60 days before development of blast crisis. Electrofocusing studies indicate the presence of three major enzymes. The level of enzyme which focused at pH 5.6 was elevated in untreated disease and rose markedly during blastic transformation. A second enzyme focused at pH 5.1 and appeared to be related to marrow erythroid turnover. A third enzyme with pI = 4.7 was elevated only during marrow regeneration which followed myelosuppressive therapy. These data suggest the enzyme with pI = 5.6 to be a specific marker in chronic granulocytic leukemia.

Fucosyltransferases↗
PubMed1979

Delineation of fucosyltransferase activities with thiol reagents.

The thiol reagent dithiothreitol inhibits the activity of a core GDP-fucose-N-acetylglucosaminide alpha-6-fucosyltransferase in plasma and blood-cell homogenates, while promoting the activity of alpha-2- and alpha-3-fucosyltransferases. The latter enzymes catalyse transfer of fucose on to terminal galactose and subterminal N-acetylglucosamine residues respectively. A thiol-blocking reagent N-ethylmaleimide does not affect the activity of the alpha-6-fucosyltransferase, but inhibits the other two enzymes. These results indicate the presence of a critical disulphide linkage in the alpha-6-fucosyltransferase, and provide a means of delineation of different fucosyltransferases.

Chemical Phenomena↗
PubMed1979

Mechanism of action of penicillamine in the treatment of avian muscular dystrophy.

Penicillamine, a cysteine analog with a reduced sulfhydryl group, has been used in this laboratory for the treatment of hereditary avian dystrophy. The drug delays the onset of symptoms and alleviates the debilitating aspects of the disease. To study the mechanism of drug action, the effects of penicillamine on white and red muscles of dystrophic chickens were examined with regard to the specific activities of the soluble enzymes glyceraldehyde-3-phosphate dehydrogenase, acetylphosphatase, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase, glutathione reductase, glutathione preoxidase, superoxide dismutase, and catalase. The sulfhydryl contents of the soluble proteins and the concentration of myoglobin were also determined. In white dystrophic muscle (pectoral), there were large alterations in the various enzymatic activities compared to normal levels. In the DISCUSSION, these changes are related to the pathogenesis of the disease and to the adaptive response for protection of the severely affected fast fibers. Red dystrophic muscles (thigh) were minimally involved, in accordance with the known sparing action of the slow fiber type. The results suggested that the disease process in dystrophic muscle may be due to oxidation of the essential sulfhydryl groups of proteins. Penicillamine may produce therapeutic effects by altering the intracellular redox status, thereby promoting better regulation of enzymatic activity, membrane stability, and improved muscle function.

Animals↗
PubMed1979

Electrofocusing patterns of fucosyltransferases in plasma of patients with neoplastic disease.

Electrofocusing patterns of plasma fucosyltransferases provide information concerning marrow status of patients with myeloproliferative disorders. Three enzymes were detected in normal plasmas using an acceptor terminating in the sequence N-acetylglucosamine-galactose. The enzyme which focused at pH 4.7 was elevated during rapid proliferation of myeloid cells, e.g., acute myelogenous leukemias and certain infectious diseases. Activity at pI = 5.1 was decreased in acute myelogenous leukemia patients, and from other observations, appears related to the level of erythropoietic activity. Acceptor studies show this enzyme to be specified by the H gene. A third enzyme focused at pH 5.5 and appeared to be correlated with a later step in granulocytes maturation. Two other plasma fucosyltransferases (pl = 5.6 and 8.3) were detected with a high-molecular-weight acceptor terminating in N-acetylglucosamine. This activity was markedly elevated during regeneration of a normal marrow population during drug-induced remission of acute myelogenous leukemia. Additional isoenzymes were detected, using this acceptor, in plasma of patients with certain solid tumors and multiple myeloma. However, the new isoelectric points observed (pH 6.0, 6.9, and 7.8) suggest these enzymes are probably not derived from hematopoietic tissues.

Acetylglucosamine↗
PubMed1978

Some properties of sialyltransferase in plasma and lymphocytes of patients with chronic lymphocytic leukemia.

Some properties of sialyltransferase activity in plasma and lymphocytes from patients with chronic lymphocytic leukemia were compared. Three distinct enzyme fractions were identified in plasma: (1) cation independent, irreversibly bound to agarose; (2) cation dependent, weakly bound to agarose; (3) strongly bound to agarose, lost upon dialysis. Lowering of the peripheral lymphocyte count by leukapheresis markedly decreased the level of serum sialyltransferase, suggesting the circulating lymphocyte is a source of the serum enzyme. The enzyme solubilized by detergent from lymphocytes showed a substantially lower Km for CMP-sialic acid than did the serum enzyme, was less sensitive to several inhibitors, was not irreversible bound to Agarose, and had a substantial cation requirement. The enzyme solubilized from the lymphocyte therefore generally resembles fraction 2 of serum.

Cations, Divalent↗
PubMed1978

Evaluation of two plasma fucosyltransferases as marker enzymes in non-Hodgkin's lymphoma.

Levels of two fusosyltransferases were measured in plasmas of patients with non-Hodgkin's lymphoma at different phases of the disease. The level of a GDP-fucose: galactoside fucosyltransferase (EC 2.4.1.69) was found elevated in nonresponding patients and was correlated with estimated tumor burden. Enzyme levels in the normal range were found in patients in remission, maintained on chemotherapy, or unmaintained. The plasma level of a GDP-fucose; N-acetylglucosaminide fucosyltransferase (EC 2.4.1.68) was elevated in all individuals receiving drug therapy regardless of diesease status, but returned to normal levels during unmaintained remissions.

Acetylglucosamine↗
PubMed1978

Guanosine diphosphate-L-fucose plasma: N-acetylglucosaminide fucosyltransferase as in index of bone marrow hyperplasia after chemotherapy.

We have measured the plasma level of a fucosyltransferase in patients with acute myelogenous leukemia and non-Hodgkin's lymphoma at various stages of the disease and in normal controls. This enzyme transfers the sugar fucose from a guanosine diphosphate-L-fucose donor to high-molecular-weight acceptors with a terminal N-acetyl-glucosamine residue. The enzyme levels of fucosyltransferase in individuals free from disease and in patients with untreated leukemia or lymphoma were comparable. A substantial increase in plasma enzyme level was measured during drug-induced remissions, three weeks after drug therapy. The enzyme level fell to the normal range during unmaintained remissions inpatients with lymphomas; comparable information for the leukemia is not available since all remissions were drug maintained. These data, together with microscopic examination of marrow samples, indicate that the level of this fucosyltransferase is correlated with regeneration of a normal marrow population after chemotherapy. The enzyme assay may prove useful in defining normal bone marrow recovery and in timing cyclic combination chemotherapy in patients with neoplastic disease.

Antineoplastic Agents↗
PubMed1977

Variation of levels of plasma guanosine diphosphate L-fucose:beta-D-galactosyl alpha-2-L-fucosyltransferase in acute adult leukemia.

We have measured plasma levels of an alpha-2-L-fucosyltransferase in 18 patients with acute adult leukemia at various clinical stages along with simultaneous bone marrow aspirations and biopsies. Patients in remission had significantly lower levels of this enzyme than did nonresponding or relapsing patients. Furthermore, plasma levels were correlated with percentage of marrow blast cells. This enzyme may serve as a biological marker for monitoring patients with acute leukemia receiving chemotherapy. It is particularly helpful as a guide to chemotherapy in patients on whom bone marrow aspirates are technically difficult to obtain.

Acute Disease↗
PubMed1975

Covalent binding of 3-pyridinealdehyde nicotinamide adenine dinucleotide and substrate to glyceraldehyde 3-phosphate dehydrogenase.

Glyceraldehyde 3-phosphate dehydrogenase (D-glyceraldehyde-3-phoshate:nicotinamide adenine dinucleotide oxidoreductase (phosphorylating), EC 1.2.1.12) forms a complex with 3-pyridinealdehyde-NAD which survives precipitation with 7% perchloric acid. The molar ratio bound 3-pyridinealdehyde-NAD to the enzyme is 2.5 to 2.9. Lactate, malate, and alcohol dehydrogenases do not form acid-precipitable complexes with 3-pyridinealdehyde-NAD. 3-Pyridinealdehyde-deamino-NAD or glyceraldehyde 3-phosphate also forms an acid-stable complex with glyceraldehyde 3-phosphate dehydrogenase; however, NAD, 3-acetylpyridine-NAD, or thionicotinamide-NAD does not produce an acid-stable complex. Incubation of the glyceraldehyde 3-phosphate dehydrogenase with glyceraldehyde 3-phosphate, acetyl phosphate, iodoacetic acid, or iodosobenzoate inhibits the formation of the acid-stable complex with 3-pyridinealdehyde-NAD. Glyceraldehyde 3-phosphate or 3-pyridinealdehyde-NAD also prevents carboxymethylation of the active site cysteine-149 by[14-C]iodoacetic acid. These studies indicate that the aldehyde group of 3-pyridinealdehyde-NAD forms a thiohemiacetal linkage with cysteine-149 which is the substrate binding site for the dehydrogenase reaction. These findings may account for the fact that 3-pyridinealdehyde-NAD strongly inhibits the dehydrogenase and esterase activities of 3-pyridinealdehyde-NAD forms a thiohemiacetal linkage with cysteine-149 which is the substrate binding site for the dehydrogenase reaction. These findings may account for the fact that 3-pyridinealdehyde-NAD strongly inhibits the dehydrogenase and esterase activities of glyceraldehyde 3-phosphate dehydrogenase which require reduced cysteine-149. However, the analogue does not inhibit the acetyl phosphates activity of the enzyme for which the active site sulfhydryl residues must be oxidized.

Aldehydes↗