Search PubMed⌕ Search

Biomedical subjects

A Orlacchio

Publications and source records attributed to A Orlacchio.

At least 127 records · Page 7Linked to original sources
PubMed1984

beta-N-acetyl-D-glucosaminidase isoenzymes by chromatofocusing from serum and skin in diabetes.

beta-N-Acetyl-D-glucosaminidase and its kinetic characteristics were determined in serum and skin from both diabetes mellitus and impaired glucose tolerance patients and controls. Mean total activity was reduced (p less than 0.05) in the skin of both patient groups. beta-N-Acetyl-D-glucosaminidase isoenzyme expression was investigated using chromatofocusing on PBE-94 coupled with automated enzyme assay. The isoenzyme profiles from serum showed two major forms (A and B) whose ratio varied from 2:1 in controls to 3:1 in diabetics. Moreover, diabetes mellitus and impaired glucose tolerance subjects displayed an intermediate (I) form. The A/B isoenzyme ratio was completely reversed in skin.

Acetylglucosaminidase↗
PubMed1984

A distinct beta-hexosaminidase isoenzyme separated from human leukemic lymphocytes and myelocytes.

The beta-hexosaminidase (EC 3.2.1.30) isoenzymes were separated on the basis of their carbohydrate moieties by an affinity chromatography using immobilized phenylboronate. Normal lymphocytes and granulocytes contain two major forms of beta-hexosaminidase, acute lymphoblastic, acute myeloblastic, chronic lymphocytic and chronic myelocytic leukemic cells contain an extra, distinct isoenzyme of beta-hexosaminidase. This extra isoenzyme may be a marker for the leukemic conversion of hematopoietic tissue.

Bone Marrow↗
PubMed1982

beta-N-acetyl-D-glucosaminidase activity levels in atrophic gastrocnemius muscle of Rana esculenta.

1. The atrophic status induced by long-term sciatectomy or tenotomy is different, since only in the first case have we found an irreversible muscular degeneration. 2. Up to 20 days after denervation or tenotomy the beta-N-acetylglucosaminidase showed increased specific activity. 3. The time-course of the beta-NAG increase is closely correlated with the loss of contractile capacity. 4. beta-NAG increases to 170% and does not fall in 20 days after cutting the nerve; but increases to 150% on day 4 and falls to 130% on day 20 after tenotomy.

Acetylglucosaminidase↗
PubMed1981

The effect of membrane phospholipid acyl-chain composition on the activity of brain-beta-N-acetyl-D-glucosaminidase.

The phospholipid acyl-chain dependence of the membrane-bound lysosomal beta-N-acetyl-D-glucosaminidase has been examined on control membranes from rat brain primary cell cultures and on membrane modified by culturing the cells in media supplemented with polyunsaturated fatty acids. The relationship between beta-N-acetyl-D-glucosaminidase activity and the membrane phospholipid acyl-chain composition has been evaluated. An increase in the unsaturation level of phosphatidyl ethanolamines and phosphatidylcholines, the most abundant phospholipids in this membrane fraction, is related to the rate of the enzymic reaction. The Arrhenius plot of the enzyme activity in modified membranes shows break-temperatures, starting from approximately 15 degrees C. The apparent activation energy below and above the break-temperature is not correlated with phospholipid acyl-chain unsaturation.

Acetylglucosaminidase↗
PubMed1980

The binding of the coenzyme pyridoxal 5'-phosphate and analogues of the substrate-coenzyme complex to tyrosine decarboxylase.

Phosphopyridoxyl derivatives, which are stable analogues of a substrate-coenzyme complex, are bound at the active site with great affinity. From a comparison of the interaction of a number of such compounds with the apoenzyme the delta G0 values for the binding of the substrate carboxy and phenyl groups and of the coenzyme aldehydic group were determined to be equal to (or more negative than) -3.8. -8.4 and -12.5kJ/mol (-0.9, -1.9 and -3kcal/mol) respectively; the delta G0 for the binding of the coenzyme phosphate group was shown to be more negative than -20.5kJ/mol (-4.9kcal/mol). Two features of the binding process of the coenzyme-substrate analogues to tyrosine decarboxylase have already been found in the case of tyrosine aminotransferase [Borri-Voltattorni, Orlacchio, Giartosio, Conti & Turano (1975) Eur. J. Biochem. 53, 151-160]: (1) in the binding of the substrate to the enzyme a significant fraction of the instrinsic delta G0 appears to be used for some associated endoergonic process; (2) the delta H0 and delta S0 of binding appear to be very sensitive indicators of the correct alignment of the substrate-coenzyme and analogues at the active site.

Binding Sites↗
PubMed1979

Studies on the cytochemical localization of adenylate-cyclase activity in Dugesia lugubris s.I.

The localization of adenylate-cyclase activity in Dugesia lugubris s.1. has been investigated cytochemically using 5'-adenylyl-imidodiphosphate as substrate. The enzyme was localized in mucous gland cells, in rhabdite cells, in intercellular spaces and also in nerve endings of this planarian. The presence of adenylate-cyclase on the membrane suggests that it might mediate different stimulus-secretion coupling by increasing cyclic AMP synthesis in specialized areas of the planarian.

Adenylyl Cyclases↗
PubMed1979

Some kinetic and other properties of the isoenzymes of aspartate aminotransferase isolated from sheep liver.

A method for the purification of mitochondrial isoenzyme of sheep liver aspartate aminotransferase (EC 2.6.1.1) is described. The final preparation is homogeneous by ultracentrifuge analyses and polyacrylamide-gel electrophoresis and has a high specific activity (182 units/mg). The molecular weight determined by sedimentation equilibrium is 87,100 +/- 680. The amino acid composition is presented; it is similar to that of other mitochondrial isoenzymes, but with a higher content of tyrosine and threonine. Subforms have been detected. On isoelectric focusing a broad band was obtained, with pI 9.14. The properties of the mitochondrial aspartate aminotransferase are compared with those of the cytoplasmic isoenzyme. The Km for L-aspartate and 2-oxoglutarate for the cytoplasmic enzyme were 2.96 +/- 0.20 mM and 0.093 +/- 0.010 mM respectively; the corresponding values for the mitochondrial form were 0.40 +/- 0.12 mM and 0.98 +/- 0.14 mM. Cytoplasmic aspartate aminotransferase showed substrate inhibition by concentrations of 2-oxoglutarate above 0.25 mM in the presence of aspartate up to 2mM. The mitochondrial isoenzyme was not inhibited in this way. Pi at pH 7.4 inhibited cytoplasmic holoenzyme activity by up to about 60% and mitochondrial holoenzyme activity up to 40%. The apparent dissociation constants for pyridoxal 5'-phosphate were 0.23 micrometer (cytoplasmic) and 0.062 micrometer (mitochondrial) and for pyridoxamine 5'-phosphate they were 70 micrometer (cytoplasmic) and 40 micrometer (mitochondrial). Pi competitively inhibited coenzyme binding to the apoenzymes; the inhibition constants at 37 degree C were 32 micrometer for the cytoplasmic isoenzyme and 19.5 micrometer for the mitochondrial form.

Amino Acids↗