In addition to glutathione (y-GluCysGly), many species of the family Poaceae have another tripeptide which has the amino acid sequence y-GluCysSer. This thiol was isolated from etiolated leaves of wheat (Triticum aestivum L. cv. Star). Its structure was elucidated by quantitative amino acid analysis after total hydrolysis and by partial hydrolysis with carboxypeptidase A and y-glutamyltranspeptidase. The content of y-GluCysSer in the leaves ofT. aestivum is increased by incubation with sulfate and is severely diminished by incubation with buthionine sulfoximine, a specific inhibitor of y-glutamylcysteine synthetase. Oxidized y-GluCysSer is reduced by yeast glutathione reductase with a rate somewhat lower than for glutathione, but the new tripeptide is not a substrate of glutathione-S-transferase from equine liver.

Lactobacillus plantarum CNRZ 1228 exhibited heme-dependent catalase activity under environmental conditions similar to those encountered during sausage fermentation. The 1,455-bp catalase gene (katL) was cloned and encoded a protein of 484 amino acids. Expression of katL in a heterologous host showed that katL encodes a functional catalase. PCR screening of selected strains of lactic acid bacteria for katL indicated the presence of similar genes in other strains of lactobacilli.

The structural genes for the two-peptide bacteriocin enterocin 1071 (Ent1071) in Enterococcus faecalis FAIR-E 309 were cloned. DNA sequence analysis showed that the enterocin 1071A (Ent1071A) peptide of strain FAIR-E 309 differed by two amino acids from the Ent1071A reported for E. faecalis BFE 1071 (E. Balla, L. M. T. Dicks, M. Du Toit, M. J. van der Merwe, and W. H. Holzapfel, Appl. Environ. Microbiol. 66:1298-1304, 2000), while the Ent1071B gene encoded identical peptides in these strains. However, resequencing of ent1071A from E. faecalis BFE 1071 showed that the Ent1071A peptide sequence reported previously was incorrect in two amino acids. Also, ent1071B in E. faecalis FAIR-E 309 encoded a prepeptide that was three amino acids shorter than that previously reported for E. faecalis BFE 1071 Ent1071B. A presumptive immunity gene (eni1071) was located downstream of the bacteriocin structural genes. This gene was cloned into the heterologous host E. faecalis ATCC 19433 and was shown to confer immunity. A truncated ABC transporter gene was located upstream of the Ent1071 structural genes.

High hydrostatic pressure is a mild technology compared with high temperatures and is commonly used for food pasteurization. Crude brain homogenates of terminally diseased hamsters infected with scrapie 263K strain were heated at 60 6C and/or pressurized up to 1000 MPa for 2 h. Prion proteins were analysed for their proteinase K sensitivity using a Western blot technique. PrP Sc pressurized with 500 MPa or above proved to be proteinase K sensitive. To test the remaining infectivity of the pressurized material, hamsters were infected intracerebrally. Results showed a greatly delayed onset of disease (from 80 up to 153 days) when samples had been pressurized at 500 MPa and above. An increase in the survival rate was also observed: 47 % survival over 180 days was seen following infection with homogenates pressurized at 700-1000 MPa.Prion diseases are associated with the accumulation of an isoform of the cellular prion protein, designated PrP Sc , after misfolding in a b-rich aggregated pathogenic multimer, which seems to be the main component of the transmissible form (Prusiner, 1991). The transmissible agent resists conventional autoclaving (Brown et al., 2000). Thus, the European Directive of 1996 recommends the use of at least 133 uC for 20 min to achieve effective inactivation during sterilization processes or rendering. Other suitable treatments, such as the combination of alkali and heat, or the use of hypochlorite solutions, although efficient, are aggressive, with a consequent loss of quality or texture in the treated tissues. Therefore, an interest in assessing the effects of unconventional milder technologies on prion stability and infectivity is growing. Milder processes would provide alternative sterilization procedures for at-risk materials and may reduce economic losses in the rendering industry. Here we report the effects of treatment with high hydrostatic pressure at 60 uC on the proteinase K (PK) sensitivity of hamster PrP Sc and the in vivo infectivity of the highpressure-treated samples.These experiments were performed with a single brain pool of the 263K strain of hamster-adapted scrapie agent. Brains containing PrP Sc were homogenized in a 1 : 10 dilution of PBS, pH 7?4, in a FastPrep cell disrupter (Qbiogene). Sets of duplicate samples were heated at 60 uC and/or pressurized up to 1000 MPa for 2 h independently. Total volumes of 250 ml of homogenate (10 %, w/v) were pressurized in a hydraulic press, U 101 (Polish Academy of Sciences, Warsaw). U 101 is a manually operated twin-piston hydraulic press (100 mm piston length, 80 mm piston movement). The vessel is a cylinder made of steel, with an inside diameter of 16 mm and 150 mm in height. The piston position is monitored with a linear transformer transducer and the pressure-measuring unit is an in-vessel manganin pressure gauge; both are digitally displayed. The pressure-transmitting medium was a 7 : 3 mixture of petroleum ether (boiling point 80-100 uC) and hydraulic oil (SAE 32). Samples were pressurized in polyethylene caps hermetically clos...

Peptides containing the cyclic product of glutamine at the N terminus are usually biologically active. If the cyclization of glutamine was associated with a volume reduction, pressure should displace the equilibrium in the direction of the lower volume. Here, results in model solutions and in whey are discussed, showing that the theorized cyclization of glutamine in Gln-His-ProNH(2) or Gln-Leu-ProNH(2) is significantly accelerated during the application of heat and even more strongly when elevated temperature and pressure combinations are used. The reaction rate depended on the intensity of the pressure treatment, the pH, and the nature of the amino acids adjacent to glutamine. The products of the reaction were identified as thyrotropin-releasing hormone (TRH) and [Leu(2)]TRH. The reported reactions could affect the naturally balanced concentration of short-chain peptides in foods and therefore induce unpredictable biological effects.