Clues to reaction specificity in PLP-dependent fold type I enzymes of monosaccharide biosynthesis

Novel functions can emerge in an enzyme family while conserving catalytic mechanism, motif or fold. PLP-dependent enzymes have evolved into seven fold types and catalyse diverse reactions using the same mechanism for the formation of external aldimine. Nucleotide sugar aminotransferases (NSATs) and dehydratases (NSDs) belong to fold type I and mediate the biosynthesis of several monosaccharides. NSATs use diverse substrates but are highly selective to the C3 or C4 carbon to which amine group is transferred. Factors responsible for reaction specificity in NSDs are known but remain unexplored in NSATs. Profile HMMs were able to identify NSATs but could not capture reaction specificity. A search for discriminating features led to the discovery of a sequence motif that is located near the pyranose binding site suggesting their role in imparting reaction specificity. Using a position weight matrix for this motif, we were able to assign reaction specificity to a large number of NSATs. Residues which upon mutation could convert NSD to NSAT have been reported in literature and we deduced that these are not conserved. This suggested the occurrence of non-generic family specific mutations underlying the evolution of dehydratases. Inferences from this analysis set way for future experiments that can shed light on mechanisms of functional diversification in enzymes of fold type I.

A Generic Family of Optimal Sixteenth-Order Multiple-Root Finders and Their Dynamics Underlying Purely Imaginary Extraneous Fixed Points

A generic family of optimal sixteenth-order multiple-root finders are theoretically developed from general settings of weight functions under the known multiplicity. Special cases of rational weight functions are considered and relevant coefficient relations are derived in such a way that all the extraneous fixed points are purely imaginary. A number of schemes are constructed based on the selection of desired free parameters among the coefficient relations. Numerical and dynamical aspects on the convergence of such schemes are explored with tabulated computational results and illustrated attractor basins. Overall conclusion is drawn along with future work on a different family of optimal root-finders.

Present state of knowledge on the family Begoniaceae CA Agardh (Magnoliopsida) of Bangladesh

The inventory and assessment of species diversity in the mono-generic family Begoniaceae C. A. Agardh of Bangladesh were made through long term field investigations, collections, identification, survey and examination of preserved herbarium specimens and review of relevant taxonomic and floristic literature. The family is recognized to be represented in the flora of Bangladesh by 19 species under the genus Begonia L. Of these, 11 species were known to be previously recorded from the area of Bangladesh, hence additional 8 species of the present account are being reported here for the first time as new records from Bangladesh, these are: Begonia grandis Dryand. ssp. holostylla Irmsch. , B. heracleifolia Cham. and Schltdl. Cult., B. maculata Raddi Cult. B. modestiflora Kurz, B. muliensis T. T. Yu. Cult., B. scintillans Dunn, B. surculigera Kurz and B. thomsonii A. DC. An enumeration of these 19 species is prepared, and each species is cited with detailed taxonomic data. All species of the Begonia L. are herbaceous in nature and possess potential economic values, viz. 11 (52%) medicinal, 5 (24%) ornamental, 3 (14%) beverage, 1 (5%) food and 1 (5%) poisonous. Determination of status of occurrence showed that 2 (10.53%) species are common, 5 (26.32%) cultivated, 9 (47.36%) threatened and 3 (15.79%) possibly extinct in Bangladesh. Field photographs and hand drawings of recorded taxa are provided.J. Biodivers. Conserv. Bioresour. Manag. 2018, 4(1): 35-46

Bifurcation sets of families of reflections on surfaces in ℝ3

We introduce a new affinely invariant structure on smooth surfaces in ℝ3 by defining a family of reflections in all points of the surface. We show that the bifurcation set of this family has a special structure at ‘ points’, which are not detected by the flat geometry of the surface. These points (without an associated structure on the surface) have also arisen in the study of the centre symmetry set; using our technique we are able to explain how the points are created and annihilated in a generic family of surfaces. We also present the bifurcation set in a global setting.