Alan Thomson

Modification of pig heart lactate dehydrogenase: A derivative possessing enhanced thermal stability

Abstract Pig heart lactate dehydrogenase ( l -lactate:NAD oxidoreductase, EC 1.1.1.27) has been modified by reaction with pentanedial to give a water-soluble product. This derivative retains 50% of initial enzymic activity, and its K m for the reduction of pyruvate is close to that of the native enzyme. Reaction with pentanedial markedly increases the thermal stability of the enzyme at pH 5.0–6.0 and at pH 9.0.

The identity of the elastase-associated acidic endopeptidase and chymotrypsin C from porcine pancreas.

The preparations of chymotrypsin C (EC 3.4.21.2) and an acidic endopeptidase from porcine pancreas have been repeated using published procedures. The acidic endopeptidase showed lower activity than chymotrypsin C in all comparative experiments, but it was possible to precipitate a fraction from the acidic endopeptidase preparation which contained all the protein and was identical with chymotrypsin C. It is concluded that the acidic endopeptidase is identical with chymotrypsin C but it is contaminated by an inert non-protein material to which it is firmly bound. The formation of a precipitate, at low ionic strength, from mixtures of chymotrypsin C and elastase (EC 3.4.21.11) is independent of the availability of the active site of either enzyme.

An ultrastructural investigation of dermatopontin-knockout mouse corneas

Introduction  The corneal stroma is composed of a network of heterotypic collagen fibrils, proteoglycans and matrix proteins. Transparency of the tissue principally requires the uniformity of fibril diameters and interfibrillar distances and the presence of a quasi‐hexagonal lattice arrangement of parallel fibrils. Keratan sulfate proteoglycans (KSPGs) have a crucial role and the KS chains are clearly required for the maintenance of transparency. Undersulfation of corneal KS results in tissue opacity and the lumican (a KSPG) knockout mouse shows corneal opacity and the disruption of collagen fibril diameters and interfibrillar distances ( Chakravarti et al. 1998 ). Biochemical analysis has shown that dermatopontin is an abundant component of the extracellular matrix and that it interacts with KSPGs via the KS chains. This study aims to determine whether dermatopontin has a direct role in corneal matrix organization by investigating the corneal ultrastructure of dermatopontin‐null (dpt–/–) mouse corneas.

Influence of Summer Episodes of Atmospheric O3 on Δ5 and Δ9 Fatty Acids in Lipids of Norway Spruce During Winter Hardening

The fatty acid composition of membrane lipids is important during the development of cold tolerance of many plants [1] often because increases in the proportion of polyunsaturated lipids retain the fluidity of membranes. For example, there is a correlation between the different degrees of winter hardiness and membrane lipid composition in Norway spruce [2]. There is also an inverse seasonal relationship in Norway spruce between short chain (C12 & C14) saturated and unsaturated C18 fatty acids in certain lipid classes [3].