Bacterial β-peptidyl aminopeptidases: on the hydrolytic degradation of β-peptides

The special chemical and biological features of β-peptides have been investigated intensively during recent years. Many studies emphasize the restricted biodegradability and the high metabolic stability of this class of compounds. β-Peptidyl aminopeptidases form the first family of enzymes that hydrolyze a variety of short β-peptides and β-amino-acid-containing peptides. All representatives of this family were isolated from Gram-negative bacteria. The substrate specificities of the peptidases vary greatly, but the enzymes have common structural properties, and a similar reaction mechanism can be expected. This review gives an overview on the β-peptidyl aminopeptidases with emphasis on their biochemical and structural properties. Their possible physiological function is discussed. Functionally and structurally related enzymes are compared to the β-peptidyl aminopeptidase

Overview of intentionally used food contact chemicals and their hazards

Food contact materials (FCMs) are used to make food contact articles (FCAs) that come into contact with food and beverages during, e.g., processing, storing, packaging, or consumption. FCMs/FCAs can cause chemical contamination of food when migration of their chemical constituents (known as food contact chemicals, FCCs) occurs. Some FCCs are known to be hazardous. However, the total extent of exposure to FCCs, as well as their health and environmental effects, remain unknown, because information on chemical structures, use patterns, migration potential, and health effects of FCCs is often absent or scattered across multiple sources. Therefore, we initiated a research project to systematically collect, analyze, and publicly share information on FCCs. As a first step, we compiled a database of intentionally added food contact chemicals (FCCdb), presented here. The FCCdb lists 12′285 substances that could possibly be used worldwide to make FCMs/FCAs, identified based on 67 FCC lists from publicly available sources, such as regulatory lists and industry inventories. We further explored FCCdb chemicals’ hazards using several authoritative sources of hazard information, including (i) classifications for health and environmental hazards under the globally harmonized system for classification and labeling of chemicals (GHS), (ii) the identification of chemicals of concern due to endocrine disruption or persistence related hazards, and (iii) the inclusion on selected EU- or US-relevant regulatory lists of hazardous chemicals. This analysis prioritized 608 hazardous FCCs for further assessment and substitution in FCMs/FCAs. Evaluation based on non-authoritative, predictive hazard data (e.g., by in silico modeling or literature analysis) highlighted an additional 1411 FCCdb substances that could thus present similar levels of concern, but have not been officially classified so far. Lastly, for over a quarter of all FCCdb chemicals no hazard information could be found in the sources consulted, revealing a significant data gap and research need.MAVA Foundation; Valery Foundatio

Impacts of food contact chemicals on human health: a consensus statement

Food Packaging Forum Foundation (FPF) and the Plastics Solution Fund (PSF

Verfahren zur Herstellung von D-Aminosäuren

Hummel H, Geueke B, Kuzu M, Gröger H. Verfahren zur Herstellung von D-Aminosäuren. 2005

Modelling of L-DOPA enzymatic oxidation catalyzed by L-amino acid oxidases from Crotalus adamanteus and Rhodococcus opacus

L-amino acid oxidases (L-AAO) are well known for their broad substrate specificity. L-amino acid oxidases from Crotalus adamanteus and Rhodococcus opacus were applied for biotransformation of 3,4-dihydroxyphenyl-L-alanine (L-DOPA) as a substrate to its corresponding alpha-keto acid. In this reaction, hydrogen peroxide formed as a by-product causes chemical decarboxylation of alpha-keto acids and acts as competitive product inhibitor. Beef liver catalase was used to decompose it.It was shown that both enzymes were able to oxidize L-DOPA to corresponding products. L-AAO from R. opacus was more specific (lower K I-DOPA value) and more active towards L-DOPA substrate than L-AAO from C. adamanteus. Its catalytic constant, k(3), estimated by Levenspiel's method, was found to be 10-fold higher than the one for L-AAO from C adamanteus. L-AAO from R. opacus exhibits slightly L-DOPA inhibition, which is not the case for L-AAO from C adamanteus.The biotransformations Of L-DOPA were carried out in batch enzyme membrane reactor (EMR), as well as in the repetitive batch EMR. The reactor and kinetics were modelled. Parameters were estimated by differential and integral method and presented in this article. (c) 2005 Elsevier B.V. All rights reserved

Beta-galactosidase from a cold-adapted bacterium: purification, characterization and application for lactose hydrolysis.

The enzyme beta-galactosidase was purified from a cold-adapted organism isolated from Antarctica. The organism was identified as a psychrotrophic Pseudoalteromonas sp. The enzyme was purified with high yields by a rapid purification scheme involving extraction in an aqueous two-phase system followed by hydrophobic interaction chromatography and ultrafiltration. The beta-galactosidase was optimally active at pH 9 and at 26 degrees C when assayed with o-nitrophenyl-beta-D-galactopyranoside as substrate for 2 min. The enzyme activity was highly sensitive to temperature above 30 degrees C and was undetectable at 40 degrees C. The cations Na+, K+, Mg2+ and Mn2+ activated the enzyme while Ca2+, Hg2+, Cu2+ and Zn2+ inhibited activity. The shelf life of the pure enzyme at 4 degrees C was significantly enhanced in the presence of 0.1% (w/v) polyethyleneimine. The pure beta-galactosidase was also evaluated for lactose hydrolysis. More than 50% lactose hydrolysis was achieved in 8 h in buffer at an enzyme concentration of 1 U/ml, and was increased to 70% in the presence of 0.1% (w/v) polyethyleneimine. The extent of lactose hydrolysis was 40-50% in milk. The enzyme could be immobilized to Sepharose via different chemistries with 60-70% retention of activity. The immobilized enzyme was more stable and its ability to hydrolyze lactose was similar to that of the soluble enzyme