Biocatalysis and biotransformation bio-inorganic chemistry. Web alert

A selection of World Wide Web sites relevant to papers published in this issue of Current Opinion in Chemical Biology.     

Amelogenins: assembly, processing and control of crystal morphology.

The remarkable properties of enamel crystals and their arrangements in an extraordinary micro-architecture are clear indications that the processes of crystal nucleation and growth in the extracellular matrix are highly controlled. The major extracellular events involved in enamel formation are: (a) delineation of space by the secretory ameloblasts and the dentino-enamel junction; (b) self-assembly of amelogenin proteins to form the supramolecular structural framework; (c) transportation of calcium and phosphate ions by the ameloblasts resulting in a supersaturated solution; (d) nucleation of apatite crystallites; and (e) elongated growth of the crystallites. Finally, during the 'maturation' step, rapid growth and thickening of the crystallites take place, which is concomitant with progressive degradation and eventual removal of the enamel extracellular matrix components (mainly amelogenins). This latter stage during which physical hardening of enamel occurs is perhaps unique to dental enamel. We have focused our in vitro studies on three major extracellular events: matrix assembly, matrix processing and control of crystal growth. This paper summarizes current knowledge on the assembly, processing and effect on crystal morphology by amelogenin proteins. The correlation between these three events and putative functional roles for amelogenin protein are discussed.     

Biocatalysis, biodegradation and bioinformatics

Biocatalysis, biodegradation and bioinformatics are prominent scientific fields in industrial microbiology and biotechnology. This paper describes developments in these fields with a focus on the role of David T Gibson as a researcher and mentor. He has pioneered studies on the mechanisms by which aerobic microorganisms transform aromatic hydrocarbons. In addition, his research has served as a model for further investigations into bacterial atrazine and dichloromethane catabolism described here. Microbial catabolism research requires information on organic chemistry, microorganisms, metabolic pathways, catabolic genes, and enzymes. These information needs are now being met more comprehensively by development of the University of Minnesota Biocatalysis/Biodegradation Database. http://dragon.labmed.umn.edu/∼lynda/index.html The database is built on the ideas championed by David Gibson that a knowledge of microbial catabolic reactions should be organized in a mechanistic fashion and in a systematic format. Received 27 March 1997/ Accepted in revised form 05 June 1997     

Interaction, uptake, and processing of LbL-coated microcarriers by PMNs

Functionalized microcarriers or hollow capsules transporting active agents offer the opportunity for drug delivery inside cells. A promising application of these drug delivery systems is the direct transport as well as the release of immobilized antiinflammatory substances (AIS) into polymorphonuclear leukocytes (PMNs), which play a key role in the course of inflammatory processes. The intended delivery of AIS into the inflamed tissue could alleviate tissue destruction taking place during chronic inflammation, as well as facilitate the termination of these processes. In this study, the capability of functionalized CaCO(3) microcarriers as AIS transporter system targeted at PMNs is investigated. The time-dependent interaction of protamine sulfate and dextran sulfate multilayer-coated 5 μm ± 1 μm CaCO(3) carriers with PMNs, in comparison with the usage of SiO(2) carriers as monodisperse model system of defined sizes (1, 3, and 5 μm), reveals a sufficient carrier/cell interaction and uptake for coincubation periods between 2 and 24 h. Furthermore, the microcarriers are exposed to an environment simulating primary granule/phagosomal conditions after phagocytosis by means of PMN stimulation. The incubation of CaCO(3) microcarriers with cell supernatant demonstrates a partial multilayer decomposition (three to five layers) within 24 h, allowing the gradual release of AIS within the short PMN life span. This observation suggests a potential application for this drug delivery system inside immunologically active cells and may open the way to new alternatives in the treatment of chronic processes.     

Phytoalexins from crucifers: synthesis, biosynthesis, and biotransformation

Phytoalexins play a significant role in the defense response of plants. These secondary metabolites, which are synthesized de novo in response to diverse forms of stress, including fungal infection, are part of the plants' chemical and biochemical defense mechanisms. Phytoalexins from crucifers are structurally and biogenetically related, but display significantly different biological activities. Here, we review work reporting the chemical structures, synthesis, biosynthesis and metabolism of cruciferous phytoalexins, as well as their biological activity towards different microorganisms.