Biomedical subjects

L Busconi

Publications and source records attributed to L Busconi.

23 records · Page 2Linked to original sources

PubMed1989

Fish muscle cytoskeletal network: its spatial organization and its degradation by an endogenous serine proteinase.

The extraction of white croaker skeletal myofibrils with KI rendered a residue in which a network of longitudinal and transverse filaments could be observed by scanning electron microscopy. A trypsin-like serine proteinase isolated from the same muscle was able to produce a complete and rapid disruption of the network, while major myofibrillar proteins were only slightly modified. This fact suggests that the disassembly of the cytoskeletal network may be an early event in the proteolysis of myofibrils. Desmin was not attacked by the proteinase under the assayed conditions, which indicates that some other unidentified component of the network would be the primary target of the action of the enzyme on myofibrils.

Animals↗

PubMed1988

Multicatalytic proteinase in fish muscle.

Proteinase II, a high-molecular-mass proteinase previously identified in white croaker skeletal muscle, was purified to apparent homogeneity by DEAE-Sephacel, phenyl-Sepharose CL 4B, and Sephacryl S-300 chromatographies. Under denaturing conditions, the enzyme dissociated into a cluster of subunits with Mr ranging from 18,000 to 26,000 and a large subunit with a Mr 60,000. The proteinase was able to hydrolyze N-terminal-blocked 4-methyl-7-coumarylamide substrates having either an aromatic amino acid (chymotrypsin-like activity) or an arginine residue (trypsin-like activity) adjacent to the fluorogenic group. The trypsin-like activity of the enzyme was inhibited by fatty acids and sodium dodecyl sulfate, whereas the chymotrypsin-like activity was stimulated by those compounds but inhibited by nonionic and cationic detergents. Several thiol reagents inhibited both proteinase II activities. However, leupeptin and Cu2+ strongly inhibited its trypsin-like activity but only slightly affected its chymotrypsin-like activity. Dithiothreitol stimulated both activities, but at different extents and in different concentration ranges. These results suggest that the enzyme is multicatalytic, having at least two different active sites.

Animals↗

PubMed1988

Activation of an alkaline proteinase from fish skeletal muscle by fatty acids and sodium dodecyl sulphate.

1. Fish skeletal muscle contains an alkaline thiol proteinase with a temperature optimum of 60 degrees C and undetectable activity below 50 degrees C. 2. The present study shows that fatty acids and sodium dodecyl sulphate (SDS) shifted the temperature-activity curve of the enzyme toward the lower temperature side. 3. All unsaturated fatty acids tested strongly stimulated proteolytic activity at 37 degrees C, whereas myristic acid was the only saturated fatty acid that produced an important degree of activation. 4. These effects could be observed at millimolar concentrations of the reagents.

Animals↗

PubMed1987

Action of a serine proteinase from fish skeletal muscle on myofibrils.

The action of a serine proteinase from fish skeletal muscle on myofibrils was studied. The enzyme was able to destroy the structural integrity of myofibrils, and to degrade both their major contractile and cytoskeletal constituent proteins. Proteolysis could be completely prevented by the addition of a trypsin inhibitor isolated from the same muscle.

Animals↗

PubMed1986

Activation of spinach chloroplast NADP-linked glyceraldehyde-3-phosphate dehydrogenase by concerted hysteresis.

Kinetic analysis of glyceraldehyde-3-phosphate dehydrogenase showed that the enhancement of the NADP-linked activity by specific chloroplast modulators is a concerted process; either a selected second metabolite or the couple dithiothreitol/thioredoxin-f lowers the concentration of primary modulators (ATP, NADPH, inorganic phosphate, 1,3-diphosphoglycerate) required for maximal stimulation (A0.5). Organic solvents also stimulate NADP-glyceraldehyde-3-phosphate dehydrogenase in the absence of any modulator; the concentration for the highest specific activity correlates inversely with the respective octanol-water partition coefficient. On the other hand, alcohols also enhance enzyme activity by lowering the A0.5 for primary modulators. Another compound--spermine--inhibits both the ATP- and the inorganic phosphate-mediated activation, but it does not influence the NADPH-induced process.

1-Propanol↗