The Experts below are selected from a list of 123 Experts worldwide ranked by ideXlab platform
John J Harada - One of the best experts on this subject based on the ideXlab platform.
-
Isocitrate Lyase and malate synthase genes from brassica napus l are active in pollen
Plant Physiology, 1994Co-Authors: James Z Zhang, Debbie Laudenciachingcuanco, L Comai, John J HaradaAbstract:To investigate if pollen possesses glyoxysomal function, we analyzed the activities of Isocitrate Lyase and malate synthase genes. Because the activities of these enzymes were exceedingly low in pollen extracts, we constructed fusion genes encoding [beta]-glucuronidase (GUS) that are regulated by Isocitrate Lyase or malate synthase promoters from Brassica napus L. to increase the sensitivity of our assays. Expression of the fusion genes in transgenic tobacco was qualitatively similar to that of the endogenous genes; GUS activity was low in dry seeds, maximal in seedlings, and very low or undetectable in leaves, indicating that the promoters are regulated correctly. We showed that Isocitrate Lyase and malate synthase genes are active at specific stages of pollen development and that their activities are not enhanced during pollen germination in transgenic tobacco. We also confirmed that the endogenous genes are active by showing that the corresponding mRNAs could be detected in pollen at specific stages of development. The activation of the Isocitrate Lyase and malate synthase genes suggests that glyoxysomal function is induced during pollen development.
-
two classes of Isocitrate Lyase genes are expressed during late embryogeny and postgermination in brassica napus l
Molecular Genetics and Genomics, 1993Co-Authors: James Z Zhang, Mariza Gomezpedrozo, Catherine S Baden, John J HaradaAbstract:We have analyzed the structure of genes encoding the glyoxylate cycle enzyme Isocitrate Lyase from Brassica napus L. and their expression during embryogeny and postgermination. Restriction mapping, nucleotide sequence, and DNA gel blot hybridization analyses of cDNA and genomic clones indicated that there are approximately six Isocitrate Lyase genes in the B. napus genome that can be divided into at least two subfamilies based upon their divergence in 5′ and 3′ untranslated regions. We showed previously that Isocitrate Lyase mRNA accumulates during late embryogeny and postgermination. Here, we present results which indicate that several Isocitrate Lyase genes are expressed at both stages of development. First, gene-specific probes were used to show that mRNAs encoded by representatives of both gene subfamilies accumulated in both late maturation stage embryos and in seedlings of B. napus. Second, a single B. napus Isocitrate Lyase gene, together with 3.5 kb and 1.4 kb of 5′ and 3′ flanking regions, respectively, was expressed in both embryos and seedlings of transgenic tobacco plants. The results indicated that accumulation of Isocitrate Lyase in late embryogeny and postgermination does not result from the alternate expression of distinct members of the gene family.
Eugenio Giachetti - One of the best experts on this subject based on the ideXlab platform.
-
Multisite inhibition of Pinus pinea Isocitrate Lyase by phosphate.
Plant physiology, 2000Co-Authors: F Ranaldi, Paolo Vanni, Eugenio GiachettiAbstract:Our results show that the phosphate ion is a nonlinear competitive inhibitor of Pinus pinea Isocitrate Lyase. In addition, this compound induces a sigmoidal response of the enzyme, which usually exhibits standard Michaelis-Menten kinetics. This peculiar behavior of P. pinea Isocitrate Lyase could be explained by a dimer (two-site) model, in which phosphate binds cooperatively, but the affinity of the vacant site for substrate (the magnesium-Isocitrate complex) remains the same. As a result, the interaction of phosphate with free enzyme produces an inhibitor-enzyme-inhibitor species that is of significant importance in determining reaction rate; a possible regulatory role of the glyoxylate cycle by inorganic phosphate is suggested. The mode of phosphate inhibition is consistent with both the mechanism for magnesium ion activation of P. pinea Isocitrate Lyase and its site heterogeneity. Our results explain the cooperative effects observed by some authors in kinetic studies of Isocitrate Lyase carried out in phosphate buffers and also account for the higher K(m) values determined by using such assay systems. Phosphate buffer should be avoided in performing Isocitrate Lyase kinetics.
F Ranaldi - One of the best experts on this subject based on the ideXlab platform.
-
Multisite inhibition of Pinus pinea Isocitrate Lyase by phosphate.
Plant physiology, 2000Co-Authors: F Ranaldi, Paolo Vanni, Eugenio GiachettiAbstract:Our results show that the phosphate ion is a nonlinear competitive inhibitor of Pinus pinea Isocitrate Lyase. In addition, this compound induces a sigmoidal response of the enzyme, which usually exhibits standard Michaelis-Menten kinetics. This peculiar behavior of P. pinea Isocitrate Lyase could be explained by a dimer (two-site) model, in which phosphate binds cooperatively, but the affinity of the vacant site for substrate (the magnesium-Isocitrate complex) remains the same. As a result, the interaction of phosphate with free enzyme produces an inhibitor-enzyme-inhibitor species that is of significant importance in determining reaction rate; a possible regulatory role of the glyoxylate cycle by inorganic phosphate is suggested. The mode of phosphate inhibition is consistent with both the mechanism for magnesium ion activation of P. pinea Isocitrate Lyase and its site heterogeneity. Our results explain the cooperative effects observed by some authors in kinetic studies of Isocitrate Lyase carried out in phosphate buffers and also account for the higher K(m) values determined by using such assay systems. Phosphate buffer should be avoided in performing Isocitrate Lyase kinetics.
-
lactate as competitive inhibitor of pinus pinea Isocitrate Lyase
Comptes rendus des séances de la Société de biologie et de ses filiales, 1995Co-Authors: F Ranaldi, C Iacoviello, P VanniAbstract:We studied the effect of L-lactate on both the cleavage and the condensation reactions of Pinus pinea Isocitrate Lyase. This compound is a competitive of Pinus pinea Isocitrate Lyase towards both Isocitrate and glyoxylate, whereas is a mixed type inhibitor towards succinate. Assuming that L-lactate acts as a glyoxylate analogue, our finding agrees with an uni-bi ordered mechanism of Isocitrate Lyase, with glyoxylate first substrate to enter the active site in the condensation reaction. Results are discussed and compared with those known in the literature about other structurally related metabolites.
Ivanhoe K. H. Leung - One of the best experts on this subject based on the ideXlab platform.
-
Acetyl-CoA-mediated activation of Mycobacterium tuberculosis Isocitrate Lyase 2.
Nature communications, 2019Co-Authors: Ram Prasad Bhusal, Wanting Jiao, Brooke X. C. Kwai, Jóhannes Reynisson, Annabelle J. Collins, Jonathan Sperry, Ghader Bashiri, Ivanhoe K. H. LeungAbstract:Isocitrate Lyase is important for lipid utilisation by Mycobacterium tuberculosis but its ICL2 isoform is poorly understood. Here we report that binding of the lipid metabolites acetyl-CoA or propionyl-CoA to ICL2 induces a striking structural rearrangement, substantially increasing Isocitrate Lyase and methylIsocitrate Lyase activities. Thus, ICL2 plays a pivotal role regulating carbon flux between the tricarboxylic acid (TCA) cycle, glyoxylate shunt and methylcitrate cycle at high lipid concentrations, a mechanism essential for bacterial growth and virulence. Isocitrate Lyase (ICL) isoforms 1 and 2 are enzymes in the glyoxylate and methylcitrate cycles that enable Mycobacterium tuberculosis (Mtb) to use lipids as a carbon source. Here the authors present the ligand-free Mtb ICL2 and acetyl-CoA bound ICL2 crystal structures, which reveal a structural reorganisation upon acetyl-CoA binding that leads to an activation of its Isocitrate Lyase and methylcitrate Lyase activities.
James Z Zhang - One of the best experts on this subject based on the ideXlab platform.
-
Isocitrate Lyase and malate synthase genes from brassica napus l are active in pollen
Plant Physiology, 1994Co-Authors: James Z Zhang, Debbie Laudenciachingcuanco, L Comai, John J HaradaAbstract:To investigate if pollen possesses glyoxysomal function, we analyzed the activities of Isocitrate Lyase and malate synthase genes. Because the activities of these enzymes were exceedingly low in pollen extracts, we constructed fusion genes encoding [beta]-glucuronidase (GUS) that are regulated by Isocitrate Lyase or malate synthase promoters from Brassica napus L. to increase the sensitivity of our assays. Expression of the fusion genes in transgenic tobacco was qualitatively similar to that of the endogenous genes; GUS activity was low in dry seeds, maximal in seedlings, and very low or undetectable in leaves, indicating that the promoters are regulated correctly. We showed that Isocitrate Lyase and malate synthase genes are active at specific stages of pollen development and that their activities are not enhanced during pollen germination in transgenic tobacco. We also confirmed that the endogenous genes are active by showing that the corresponding mRNAs could be detected in pollen at specific stages of development. The activation of the Isocitrate Lyase and malate synthase genes suggests that glyoxysomal function is induced during pollen development.
-
two classes of Isocitrate Lyase genes are expressed during late embryogeny and postgermination in brassica napus l
Molecular Genetics and Genomics, 1993Co-Authors: James Z Zhang, Mariza Gomezpedrozo, Catherine S Baden, John J HaradaAbstract:We have analyzed the structure of genes encoding the glyoxylate cycle enzyme Isocitrate Lyase from Brassica napus L. and their expression during embryogeny and postgermination. Restriction mapping, nucleotide sequence, and DNA gel blot hybridization analyses of cDNA and genomic clones indicated that there are approximately six Isocitrate Lyase genes in the B. napus genome that can be divided into at least two subfamilies based upon their divergence in 5′ and 3′ untranslated regions. We showed previously that Isocitrate Lyase mRNA accumulates during late embryogeny and postgermination. Here, we present results which indicate that several Isocitrate Lyase genes are expressed at both stages of development. First, gene-specific probes were used to show that mRNAs encoded by representatives of both gene subfamilies accumulated in both late maturation stage embryos and in seedlings of B. napus. Second, a single B. napus Isocitrate Lyase gene, together with 3.5 kb and 1.4 kb of 5′ and 3′ flanking regions, respectively, was expressed in both embryos and seedlings of transgenic tobacco plants. The results indicated that accumulation of Isocitrate Lyase in late embryogeny and postgermination does not result from the alternate expression of distinct members of the gene family.
