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I G Sumner

Publications and source records attributed to I G Sumner.

25 records · Page 2Linked to original sources
PubMed1991

Changes in activity of porcine phospholipase A2 brought about by charge engineering of a major structural element to alter stability.

We have modified the stability of porcine phospholipase A2 by charge engineering. The mutations are situated at the N-terminal of a major helix and are N89D and N89D/E92Q. This engineering has significantly altered the activity of the enzyme to aggregated and monomeric substrates. A N89D/E92K mutant is more stable but considerably less active than wild type. An N89D mutant is more stable and of similar activity to wild type. The substantial change in activity may be due to direct interaction of residue 92 with aggregated substrate or may be via second calcium binding. Second calcium binding may be more probable as activity against monomers is also affected. Additional calcium binding may therefore be an important way of manipulating the activity of phospholipase A2.

Animals↗
PubMed1990

Preliminary crystallographic data for protease omega.

Protease omega from Carica papaya L. has been purified and crystallized. The crystals are trigonal, space group P3(1)12 (or P3(2)12), with a = 7.42 +/- 0.02 nm, c = 7.79 +/- 0.02 nm with one molecule in the asymmetric unit. The crystals diffract to 0.19-nm resolution using synchrotron radiation.

Crystallography↗
PubMed1988

The electrostatic fields in the active-site clefts of actinidin and papain.

The active sites of actinidin (EC 3.4.22.14) and papain (EC 3.4.22.2) display different reactivity characteristics to probes targeted at the active-site cysteine residue despite the close structural similarity of their active sites. The calculated electrostatic fields in the active-site clefts of actinidin and papain differ significantly and may explain the reactivity characteristics of these enzymes. Calculation of electrostatic potential also focuses attention on the electrostatic properties that govern formation of the active-site thiolate-imidazolium ion-pair. These calculations will guide the modification of the pH-activity profile of the cysteine proteinases by site-directed mutagenesis.

Binding Sites↗
PubMed1983

Characterisation of hepatocyte sub-populations generated by centrifugal elutriation.

We describe protocols for the fractionation of isolated hepatocytes into eight sub-populations using centrifugal elutriation. The distribution of fluorescein isothiocyanate and acridine orange in hepatocytes prepared from livers pre-perfused with one of these dyes is described and used as an indicator of acinar zone derivation for each population. The cytochrome P-450 content and response to induction by 3-methylcholanthrene and phenobarbitone; the distribution of lactate dehydrogenase, glucose-6-phosphatase, pyruvate kinase and tyrosine aminotransferase activities in the sub-populations is also reported. A marked asymmetry of distribution in all these activities was observed. On the basis of putative zone derivations (based on data of fluorescent dye distribution) of eight factors studied, the distributions of six were consistent with the sub-populations being derived from different acinar zones. Two major discrepancies were noted however, the distribution of pyruvate kinase activity and the response of the sub-populations to phenobarbitone. We conclude from this study that while a metabolic heterogeneity was revealed in the sub-populations generated, further characterisation is required to determine whether acinar zone separation has occurred and if so to what extent.

Acridine Orange↗