Biochemical Characterization of Recombinant UDPG-Dependent IAA Glucosyltransferase from Maize (Zea mays)

International Journal of Molecular Sciences

Maciej Ostrowski¹  Anna Ciarkowska¹  Anna Kozakiewicz² 

[1] Faculty of Biological and Veterinary Sciences, Nicolaus Copernicus University in Toruń, 87-100 Toruń, Poland;Faculty of Chemistry, Nicolaus Copernicus University in Toruń, 87-100 Toruń, Poland;

关键词: auxin conjugate;    indole-3-acetic acid;    UDPG-dependent IAA glucosyltransferase;    enzyme modulators;    inhibitor–enzyme interaction;   

DOI  :  10.3390/ijms22073355

来源: DOAJ

【 摘 要 】

Here, we report a biochemical characterization of recombinant maize indole-3-acetyl-β-d-glucose (IAGlc) synthase which glucosylates indole-3-acetic acid (IAA) and thus abolishes its auxinic activity affecting plant hormonal homeostasis. Substrate specificity analysis revealed that IAA is a preferred substrate of IAGlc synthase; however, the enzyme can also glucosylate indole-3-butyric acid and indole-3-propionic acid with the relative activity of 66% and 49.7%, respectively. K_M values determined for IAA and UDP glucose are 0.8 and 0.7 mM, respectively. 2,4-Dichlorophenoxyacetic acid is a competitive inhibitor of the synthase and causes a 1.5-fold decrease in the enzyme affinity towards IAA, with the K_i value determined as 117 μM, while IAA–Asp acts as an activator of the synthase. Two sugar-phosphate compounds, ATP and glucose-1-phosphate, have a unique effect on the enzyme by acting as activators at low concentrations and showing inhibitory effect at higher concentrations (above 0.6 and 4 mM for ATP and glucose-1-phosphate, respectively). Results of molecular docking revealed that both compounds can bind to the PSPG (plant secondary product glycosyltransferase) motif of IAGlc synthase; however, there are also different potential binding sites present in the enzyme. We postulate that IAGlc synthase may contain more than one binding site for ATP and glucose-1-phosphate as reflected in its activity modulation.

【 授权许可】

Unknown