Showing papers on "Isovitexin published in 1975"

Dominance relationships between allelic glycosyltransferase genes in Melandrium: An enzyme-kinetic approach

Abstract: In the petals of Melandrium the glycosylation of the 7-hydroxylgroup of isovitexin is governed by a series of 4 multiple alleles: gG, g, gX, and $${\text{g}}^{{\text{X}}^{\text{1}} }$$ Gene gG is the structural gene for UDP-glucose: isovitexin 7-0-glucosyltransferase; the alleles gX and $${\text{g}}^{{\text{X}}^{\text{1}} }$$ are structural genes for UDP-xylose: isovitexin 7-0-xylosyltransferase Gene g is inactive and does not produce a functional glycosyltransferase In the presence of both gene gG and its allele gX the product of gene gX (isovitexin 7-0-xyloside) is not detectable In this respect gene gG is dominant over its allele gX In petal extracts of these gG/gX plants, xylosyltransferase, as well as glucosyltransferase, can be detected The dominance is therefore not a consequence of transcriptional and/or translational control Enzyme kinetic experiments demonstrated that inhibition of xylosyltransferase by the end product of glucosyltransferase did not occur Comparison of the enzyme kinetic parameters revealed that dominance is probably caused by differences in Vmax between the two enzymes, both working at saturating isovitexin concentrations A competition model is proposed which explains why the amounts of isovitexin 7-0-xyloside in gXgX and isovitexin 7-0-glucoside in gGgG plants are about the same, whereas in gGgX plants isovitexin 7-0-xyloside escapes dejection This competition model is supported by the enzyme kinetic results found with the codominant allele $${\text{g}}^{{\text{X}}^{\text{1}} }$$