Lipase-mediated Resolution of Branched Chain Fatty Acids

Branched chain fatty acids (BCFAs) are fatty acids substituted with alkyl groups. Many of them are chiral and therefore occur in two enantiomeric forms. This review describes their occurrence in Nature, their biosynthesis, their properties as flavours, and their enzymatic kinetic resolution. Many lipases are able to separate the enantiomers of BCFAs, in hydrolysis, esterification or transesterification reactions. Very often, the stereoselectivity of these reactions is remarkably high, even when the chiral carbon atom is remote from the carboxylic acid group.     

Nodulin gene expression during soybean (Glycine max) nodule development

In vitro translation products of total RNA isolated from soybean nodules at successive stages of nodule development were analyzed by two-dimensional gel electrophoresis. In that way the occurrence of over 20 mRNAs specifically transcribed from nodulin genes was detected. The nodulin genes could be divided into two classes according to the time of expression during nodule development. Class A comprises at least 4 nodulin mRNAs which are found when a globular meristem is present in the root cortex. These class A nodulin genes have a transient expression. Class B nodulin genes are expressed when the formation of a nodule structure has been completed. Bradyrhizobium japonicum nod ⁺ fix^-mutants, with large deletions spanning the nif H,DK region, still induced nodules showing normal expression of all nodulin genes, indicating that the nif H,DK region is not involved in the induction of nodulin genes. In nodules induced by Bradyrhizobium japonicum nod ⁺ fix^-mutant HS124 the bacteria are rarely released from the infection thread and the few infected cells appear to be collapsed. All class A and class B nodulin genes are expressed in HS124 nodules with the exception of 5 class B genes.     

Comparison of pherograms (plasma proteins, hemoglobins) in three species of Textor Temminck (Aves Ploceidae from Kinshasa region, Republic of Za?re)

The plasmic proteinograms got in agar-gel with adult subjects of three species of weavers offer clear similitude to each other and allow only very unusually a separation of the three species. Intraspecific variations in the three species appear on the level of zones a-b-c-d (alpha-globulins). None of these variations could be referred to a particular physiologic state. In the young weavers, we don't meet the beta-gamma-globulins h-i again. In those, the proteins concentration is very low and the haematocrit not very high. The two haemoglobinic fractions are lowly concentrated. Their relative concentration are in relation inverse to the concentrations observed in the grown-up subjects.     

Etude des enzymes digestifs chez pila léopoldvillensis Putz. (Moll. Gastéropode) I° partie: cellulase et alginase

Summary Cellulolytic and alginolytic enzymes have been determined in the digestive tract of the Gasteropode Pila leopoldvillensis Putz.The optimum pH lies between 5,4 and 5,5 for cellulase and at 7,2 for alginase. The maximal activity of cellulase was found in the gut content and that of alginase at the level of the hépato-pancréas and in the stomach content.Owing to the feeding habits of Pila, the presence of cellulase is not surprising. Taking into account the known distribution of alginates (in marine brown algae), the occurrence of alginase seem at least curious. It must however be born in mind that many marine molluscs have this enzyme.     

Halogenation and Oxidation Reactions with Haloperoxidases

Haloperoxidases are enzymes which catalyze the incorporation of halogen atoms into organic molecules. They are found throughout nature, playing a major role in the defence system of many organisms. Their reaction mechanisms as well as their use as catalysts for halogenation and oxidation reactions on laboratory and industrial scales are discussed. Up to now, selective halogenation reactions have only been reported for the chloroperoxidase from Pseudomonas pyrrocinia. The usefulness of the other enzymes is based on their ability to produce hypohalous acid (HOX) in a controllable way, allowing the smooth (yet nonselective) halogenation of electron-rich substrates. On the other hand, it has been shown recently that some haloperoxidases can stereoselectively convert sulfides and alkenes into their corresponding homochiral oxides. Therefore, these enzymes will undoubtedly gain importance in the near future.