English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

Two side-chain-thionated beta-lactams, a penicillin and a cephalosporin, have been prepared and found to be not significantly poorer as substrates of typical serine (classes A and C) beta-lactamases than are their oxo analogues. This result is interpreted to mean that any hydrogen-bonding site on these enzymes for the beta-lactam side-chain amide carbonyl group must be flexible and is more likely to be a passive rather than active or essential feature of the active site. Previously, data from crystal structures and site-directed mutagenesis had suggested that the side chain of Asn-132 of class-A beta-lactamases, a component of the conserved SDN loop, forms a hydrogen bond with the side-chain carbonyl of the beta-lactam substrate and may provide significant transition-state stabilization during catalysis. The thionocephalosporin was also equally as good as its oxo analogue as a substrate of the class-B beta-lactamase II of Bacillus cereus and not significantly less effective as an inhibitor of the Streptomyces R61 DD-peptidase; a tight hydrogen-bond donor site for the beta-lactam side-chain amide is apparently not present in these enzymes either.

biochemical journal

Effect of side-chain amide thionation on turnover of <i>β</i>-lactam substrates by <i>β</i>-lactamases. Further evidence on the question of side-chain hydrogen-bonding in catalysis

Effect of side-chain amide thionation on turnover of β-lactam substrates by β-lactamases. Further evidence on the question of side-chain hydrogen-bonding in catalysis