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Title: Structural basis for substrate recognition and inhibition of prephenate aminotransferase from Arabidopsis

Aromatic amino acids are protein building blocks and precursors to a number of plant natural products, such as the structural polymer lignin and a variety of medicinally relevant compounds. Plants make tyrosine and phenylalanine by a different pathway from many microbes; this pathway requires prephenate aminotransferase (PAT) as the key enzyme. Prephenate aminotransferase produces arogenate, the unique and immediate precursor for both tyrosine and phenylalanine in plants, and also has aspartate aminotransferase (AAT) activity. The molecular mechanisms governing the substrate specificity and activation or inhibition ofPATare currently unknown. Here we present the X‐ray crystal structures of the wild‐type and various mutants ofPATfromArabidopsis thaliana(AtPAT). Steady‐state kinetic and ligand‐binding analyses identified key residues, such as Glu108, that are involved in both keto acid and amino acid substrate specificities and probably contributed to the evolution ofPATactivity among class IbAATenzymes. Structures of AtPATmutants co‐crystallized with either α‐ketoglutarate or pyridoxamine 5′‐phosphate and glutamate further define the molecular mechanisms underlying recognition of keto acid and amino acid substrates. Furthermore, cysteine was identified as an inhibitor ofPATfromA. thaliana and Antirrhinum majusplants as well as the bacteriumChlorobium tepidum, uncovering a potential new effector ofPAT.

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Author(s) / Creator(s):
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Publisher / Repository:
Date Published:
Journal Name:
The Plant Journal
Page Range / eLocation ID:
p. 304-314
Medium: X
Sponsoring Org:
National Science Foundation
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