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Results for “Spheroplasts”

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PubMed1976

Purification of the membrane-bound DD-carboxypeptidase of the unstable spheroplast L-form of Proteus mirabilis by affinity chromatography. Non-competitive inhibition of the enzyme by penicillins and low stability of the enzyme-inhibitor complex.

Membrane-bound DD-carboxypeptidase of the unstable L-form of Proteus mirabilis was solubilized by the non-ionic detergent Genapol X-100 and purified to protein homogeneity by affinity chromatography on ampicillin bound to succinyl-aminododecyl-cellulose. The purified enzyme with a molecular weight of 43000 is inhibited non-competitively by penicillin G and carbenicillin, indicating a function of the penicillins as allosteric inhibitors. Sensitivity of the enzyme to penicillins is only moderate with a Ki of 1 muM for penicillin G. Breakdown of.the enzyme-inhibitor complex EI with different penicillins occurs rapidly with reappearance of active DD-carboxypeptidase. The half-life of EI with penicillin G is 5.5 min at 30 degrees C and 3.5 min at 37 degrees C, 10--1000-fold shorter than EI half-lives of DD-carboxypeptidases in several other bacteria. The low stability of the enzyme-inhibitor complex and the moderate penicillin sensitivity appear to be the basis for the continued activity of DD-carboxypeptidase during growth of the L-form and synthesis of peptidoglycan in the presence of high concentrations of penicillin.

Carboxypeptidases↗
PubMed1999

The spheroplast lysis assay for yeast in microtiter plate format.

A yeast lysis assay in the microtiter plate format improved precision and throughput and led to an improved algorithm for estimating lag time. The assay reproducibly revealed differences of 10% or greater in the maximal lysis rate and 50% or greater in the lag time. Clonal differences were determined to be the major source of variation. Microtiter-based assays should be useful for screening for drug susceptibility and for analyzing mutant phenotypes.

Cell Wall↗