Regulation Of Biosynthetic Enzymes Research Articles

First person – Jacqueline Simonet

ABSTRACTFirst Person is a series of interviews with the first authors of a selection of papers published in Biology Open, helping early-career researchers promote themselves alongside their papers. Jacqueline Simonet is first author on ‘CTP synthase polymerization in germline cells of the developing Drosophila egg supports egg production’, published in BiO. Jacqueline conducted the research described in this article while a postdoctoral research associate in Jeffrey Peterson's lab at Fox Chase Cancer Center, Philadelphia, PA and is now a Visiting Assistant Professor at Arcadia University, PA, investigating the regulation of cell metabolism, particularly the regulation of biosynthetic enzymes by filamentation using Drosophila as a model system.

Structural comparison of oxidized and reduced FKBP13 from Arabidopsis thaliana

AtFKBP13, an immunophilin in the chloroplast thylakoid lumen, participates in redox-regulatory processes via a pair of conserved disulfide bonds that are present at the N- and C-termini of the protein. Characterization of this protein by structural and biochemical analysis has revealed a novel mechanism of redox regulation in the thylakoid lumen. The protein is active in its oxidized form but is inactivated after reduction by the thioredoxin system. This is in sharp contrast with the regulation of biosynthetic enzymes in the stroma of the chloroplast, where reduction of enzymes by thioredoxin activates their function. To understand how the reduced form of AtFKBP13 is stabilized and how reduction of the cysteine residues affects the molecular properties of the enzyme, we determined the crystal structure of reduced AtFKBP13 at 1.88 A. Comparison of the reduced structure and the oxidized form that we published earlier shows rearrangements in redox site regions, readjustments of hydrogen-bonding interactions and the secondary structure of the active site residues 50-53, and reduced accessibility of the catalytic residues involved in the peptidyl proline isomerase (PPIase) activity of this enzyme. We propose that redox-linked changes in the secondary structure of the PPIase domain are responsible for significant functional differences in this protein in the reduced and oxidized states.

Polyamine content and metabolism in Arabidopsis thaliana and effect of spermidine on plant development

In this work, we have investigated polyamine levels (free and conjugated), activities and regulation of biosynthetic enzymes in different organs of Arabidopsis thaliana L. (ecotype Columbia) wild-type. When plants were grown at 0.5 mM spermidine, a different morphology was observed, with shorter stalks and darker green leaves. Spermidine-treated plants clearly take up this polyamine from the medium against a concentration gradient and redistribute it in the different organs both in free and conjugated form. In addition, in most plant organs, but especially in seedling cotyledons, the uptaken spermidine was converted to putrescine predominantly in the free form. N 8-Acetylspermidine was also absorbed by Arabidopsis seedlings. The successive increase of putrescine suggests the presence of an interconversion of acetylspermidine to putrescine via a putative polyamine oxidase. Arginine decarboxylase (ADC, EC 4.1.1.19), ornithine decarboxylase (ODC, EC 4.1.1.17) and S-adenosylmethionine decarboxylase (SAMDC, EC 4.1.1.50) activities were determined in control and spermidine-treated seedling cotyledons and flowering plant leaves. ADC activity was equally distributed between soluble and particulate fraction, while ODC was mainly localised in the particulate one. ODC seemed to be the main enzyme involved in putrescine biosynthesis. SAMDC mRNA transcript progressively increased going from cotyledons to flowering plant stage; spermidine synthase (EC 2.5.1.16) transcript was highest in rosette plant leaves followed by flowering stalks. SAMDC transcript levels were generally lower in spermidine-supplemented plants with respect to controls, on the contrary spermidine synthase mRNA was not affected by the treatment.

Correction - Interaction between Energy Charge and Product Feedback in the Regulation of Biosynthetic Enzymes. Aspartokinase, Phosphoribosyladenosine Triphosphate Synthetase, and Phosphoriboyl Pyrophosphate Synthetase

Correction - Interaction between Energy Charge and Product Feedback in the Regulation of Biosynthetic Enzymes. Aspartokinase, Phosphoribosyladenosine Triphosphate Synthetase, and Phosphoriboyl Pyrophosphate Synthetase

Interaction between energy charge and product feedback in the regulation of biosynthetic enzymes. Aspartokinase, phosphoribosyladenosine triphosphate synthetase, and phosphoribosyl pyrophosphate synthetase.

Interaction between energy charge and product feedback in the regulation of biosynthetic enzymes. Aspartokinase, phosphoribosyladenosine triphosphate synthetase, and phosphoribosyl pyrophosphate synthetase.