Biomedical subjects

D S Scher

Publications and source records attributed to D S Scher.

2 recordsLinked to original sources

PubMed1994

Isotype choice for chimeric antibodies affects binding properties.

Construction of a series of chimeric antibodies (murine variable region and human constant region) derived from the murine antibody BIRR1, which recognizes intercellular adhesion molecule 1 (ICAM-1), has revealed differences in the relative binding abilities of the chimeric antibody to antigen. The chimeric antibodies show a ranking of their ability to compete with BIRR1 for antigen on the surface of cells with the order BIRR1 = cIgG1 (100%) > cIgG4 (30%) > cIgG2 (10%) as demonstrated by solid-phase competitive enzyme-linked immunosorbent assay. Papain digestion yielded Fab fragments that were purified to homogeneity. Competitive enzyme-linked immunosorbent assay showed that the chimeric and murine Fab binding constants were equivalent. A solution-phase binding assay (analyzed by size exclusion high performance liquid chromatography) between the intact mAbs and recombinant soluble ICAM-1 further established that the binding constants involving the Fab arms of the two antibodies were equivalent. In summary, the murine and chimeric anti-ICAM-1 antibodies bind cellular ICAM-1 with equivalent affinities but with differing avidities.

Animals↗

PubMed1989

3-Hydroxy-3-methylglutaryl coenzyme A lyase from Pseudomonas mevalonii.

HMG-CoA lyase, the putative second intracellular enzyme of mevalonate catabolism in Pseudomonas mevalonii (which we previously referred to as Pseudomonas sp. M (Gill et al. (1984) J. Bacteriol. 160, 294-298, Gill et al. (1985) J. Biol. Chem. 250, 9393-9398 and Sherban, M.S., Thesis, Purdue University), was purified 650-fold from cell extracts to a specific activity of 22 mumol acetyl-CoA formed per min per mg protein. This represents the first published report of the partial purification and characterization of an HMG-CoA lyase from a prokaryotic source. Cleavage of HMG-CoA produced acetyl-CoA and acetoacetate. Activity was optimal at pH 8.8 and was undetectable at or below pH 6.5. The estimated Km for S-HMG-CoA was 100 microM. Both a reduced thiol and Mg2+ or Mn2+ were required for activity. While Mn2+ was preferred at low concentrations, 1 mM or higher concentrations of either cation supported the same maximum velocity. An apparent native Mr of 40,400 +/- 3100 was estimated from gel filtration and sucrose density gradient ultracentrifugation data.

Cations, Divalent↗