Two biological fluids, namely hemolymph and digestive fluid from the larval stage of Rhynchophorus palmarum Linneaus, a serious pest in agroecosystem exploiting oil palm, were screened for hydrolytic activities, by the use of synthetic and natural glycoside substrates. Several exo and endoglycosidase activities were observed but, the interesting alpha-mannosidase activity (0.41 +/- 0.04 UI) had attracted our attention. So, we have previously demonstrated that this activity harbours four distinctive alpha-mannosidase isoforms named RpltM, RplM1, RplM2 and RplM3. We have extended this work to determine the ability of these enzymes to catalyze synthesis reactions. Finally, we have revealed that, alpha-mannosidases from the digestive fluid of R. palmarum larvae catalyze transmannosylation reactions. The stability of the enzymes and the optimization of the transfer product yield were studied as functions of pH, enzyme unit, starting concentration of donor or acceptor and time. It was shown that, in experimental optimum conditions, average yields of 12.34 +/- 0.75, 12.15 +/- 0.79, 5.59 +/- 0.35 and 8.43 +/- 0.50% were obtained for the alpha-mannosidases RpltM, RplM1, RplM2 and RplM3, respectively. On the basis of this work, alpha-mannosidases from the digestive fluid of Rhynchophorus palmarum larvae appear to be a valuable tool for the preparation of neoglycoconjugates.

This study aimed at exploring for new natural peptides with strong inhibitory capabilities on α-amylase, the main metabolic enzyme that regulates mellitus diabetes, in order to contribute in controlling this global pandemic. It has consisted in heat shock (to 60˚C, 70˚C, 80˚C, 90˚C and 100˚C for 10, 20 and 30 minutes) of crude proteins extracted from biomass and extracellular parts of Saccharomyces cerevisiae under cultivation, and from the digestive fluid of the giant snail Achatina achatina, and in-vitro assays of the resulting solutions, as effectors, in human α-amylase catalyzing reactions. The results showed