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T D Hennessey

Publications and source records attributed to T D Hennessey.

8 recordsLinked to original sources
PubMed1983

Antibacterial activity and uptake into Escherichia coli of backbone-modified analogues of small peptides.

Analogues of di- and tripeptides in which the peptide backbone is modified have been examined for antibacterial activity in vitro, and for uptake into Escherichia coli. Aminoxy and hydrazino types, in which the peptide linkage is replaced, respectively, by -CO-NHO- or -CO-NH-NH-, were active against E. coli, Staphylococcus aureus, and Salmonella dublin; retro, alpha-aza, tetrazole, and hydroxamic types were inactive. Highest potency against all three species was found in aminoxy analogues containing D-2-aminoxypropionic acid (D-OAla) residues, Ala-D-OAla being active at less than 1 mg 1-1. Uptake into E. coli was seen with all active types, but, with the exception of hydroxamic analogues not with the inactive types. Following uptake the toxic analogues were rapidly hydrolysed and the constituent amino acid residues underwent exodus. The substrate specificities of the peptide transport systems have been further defined on the basis of our results.

Alanine↗
PubMed1979

Regulation of glucosyl- and fructosyltransferase synthesis by continuous cultures of Streptococcus mutans.

Streptococcus mutans strains Ingbritt, and its derivative B7 which had been passaged through monkeys, have been used to investigate how the synthesis of extracellular glucosyl- and fructosyltransferases is regulated. The most active enzyme from carbon-limited continuous cultures was a fructosyltransferase; enzymes catalysing the formation of water-insoluble glucans from sucrose were relatively inactive. Dextransucrase (EC 2.4.1.5), which catalyses soluble glucan synthesis, was most active in the supernatant fluid from cultures grown with excess glucose, fructose or sucrose, but full activity was detected only when the enzyme was incubated with both sucrose and dextran. Little dextransucrase activity was detected in carbon-limited cultures. It is concluded that glucosyl- and fructosyltransferases are constitutive enzymes in that they are synthesized at similar rates during growth with an excess of the substrate or of the products of the reactions which they catalyse. Although the Ingbritt strain was originally isolated from a carious lesion, it is now a poor source of glucosyltransferase activity. Glucosyltransferases were extremely active in cultures of a recent clinical isolate, strain 3209, and were apparently induced during growth with excess glucose.

Culture Media↗
PubMedDate not supplied

[Chlorhexidine].

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Bacteria↗