Leaf beetles have developed an impressive repertoire of toxins and repellents to defend themselves against predators. Upon attack, the larvae discharge small droplets from glandular reservoirs on their back. The reservoirs are “bioreactors” performing the late reactions of the toxin-production from plant-derived or de novo synthesised glucosides. The import of the glucosides into the bioreactor relies on a complex transport system. Physiological studies revealed a functional network of transporters guiding the glucosides through the larval body into the defensive system. The first of the involved transporters has been identified and characterised concerning selectivity, tissue distribution, and regulation. The development of a well-tuned transport system, perfectly adjusted to the compounds provided by the food plants, provides the functional basis for the leaf beetle defenses and their local adaptation to their host plants.

Certain strains of the soil microorganism Streptomyces produce an antibiotic, fosfomycin [(1 R,2 S)-epoxypropylphosphonic acid], which is effective against both Gram-positive and Gram-negative pathogens by inhibiting the first committed step in cell-wall biosynthesis. Fosfomycin resistance proteins are metallo-enzymes that are known to inactivate the antibiotic by the addition of nucleophiles such as water, glutathione (GSH), l-cysteine and bacillithiol (BSH) to the oxirane ring of the molecule. Progress in the characterisation of FosB-type fosfomycin resistance proteins found in many Gram-positive organisms has been slow. This paper provides a brief description of the diversity of fosfomycin resistance proteins in general and, more specifically, new data characterising the substrate selectivity, structure, mechanism and metal-ion dependence of FosB enzymes from pathogenic strains of Staphylococcus and Bacillus. These new findings include the high-resolution X-ray diffraction structures of FosB enzymes from Staphylococcus aureus and Bacillus cereus in various liganded states and kinetic data that suggest that Mn(II) and BSH are the preferred divalent cation and thiol substrate for the reaction, respectively. The discovery of the inhibition of the enzyme by Zn(II) led to the determination of a ternary structure of the FosB·Zn(II)·fosfomycin·l-Cys complex which reveals both substrates present in a pose prior to reaction.

Catfish are hardy in nature and it is not known whether the presence of efficient detoxication enzymes is partly responsible for this trait. To investigate this, we have assessed induction of glutathione transferase (GST) in 10-week-old juvenile catfish (Clarias gariepinus) exposed to graded concentrations of lindane, an organochlorine insecticide, and characterised the purified enzyme from groups having the highest and statistically significant induction. Some of the unique properties observed for the purified enzyme are a high Km (1.72±0.21mM) for the electrophilic model substrate, 1-chloro-2,4-dinitrobenzene (CDNB) and a very low catalytic rate (Vmax=0.130±0.010units/mg protein). The kcat/Km being 55.4±0.2M−1s−1. The enzyme is present in high concentration in the organism, the main isoform accounts for about 5.6% of the total soluble protein, probably to compensate for the observed kinetic imperfection. Since these properties are generally not known for a detoxication enzyme, we suggest that they may form part of the organism׳s own adaptation to its polluted environment.

The field of biothermodynamics encompasses physical property measurements on biochemical and biological systems. This chapter reviews the status of standards documents that are pertinent to biothermodynamics as well as recommendations that have been made for the reporting of experimental results. The importance of standards in nomenclature, symbols, units, and uncertainties is discussed and a summary of sources of data for biochemical substances and reactions is given.

International audience

This review describes the key steps and methods which are used to develop enzyme assays suitable for high-throughput screening (HTS) applications. The goals of HTS enzyme assays are defined relative to lower-throughput bench top assays and important aspects which go into constructing robust and sensitive enzyme assays are described. Methods that have been applied to common enzyme classes are reviewed and pitfalls related to assay artifacts are discussed. We also suggest a reporting format to describe the steps in HTS enzyme assays.