7MES image
Entry Detail
PDB ID:
7MES
Keywords:
Title:
Structure of ALDH4A1 complexed with trans-4-Hydroxy-D-proline
Biological Source:
Source Organism:
Host Organism:
PDB Version:
Deposition Date:
2021-04-07
Release Date:
2021-06-09
Method Details:
Experimental Method:
Resolution:
1.37 Å
R-Value Free:
0.17
R-Value Work:
0.16
R-Value Observed:
0.16
Space Group:
P 21 21 21
Macromolecular Entities
Polymer Type:polypeptide(L)
Description:Delta-1-pyrroline-5-carboxylate dehydrogenase, mitochondrial
Chain IDs:A, B
Chain Length:563
Number of Molecules:2
Biological Source:Mus musculus
Primary Citation
Structural basis for the stereospecific inhibition of the dual proline/hydroxyproline catabolic enzyme ALDH4A1 by trans-4-hydroxy-L-proline.
Protein Sci. 30 1714 1722 (2021)
PMID: 34048122 DOI: 10.1002/pro.4131

Abstact

Aldehyde dehydrogenase 4A1 (ALDH4A1) catalyzes the final steps of both proline and hydroxyproline catabolism. It is a dual substrate enzyme that catalyzes the NAD+ -dependent oxidations of L-glutamate-γ-semialdehyde to L-glutamate (proline metabolism), and 4-hydroxy-L-glutamate-γ-semialdehyde to 4-erythro-hydroxy-L-glutamate (hydroxyproline metabolism). Here we investigated the inhibition of mouse ALDH4A1 by the six stereoisomers of proline and 4-hydroxyproline using steady-state kinetics and X-ray crystallography. Trans-4-hydroxy-L-proline is the strongest of the inhibitors studied, characterized by a competitive inhibition constant of 0.7 mM, followed by L-proline (1.9 mM). The other compounds are very weak inhibitors (approximately 10 mM or greater). Insight into the selectivity for L-stereoisomers was obtained by solving crystal structures of ALDH4A1 complexed with trans-4-hydroxy-L-proline and trans-4-hydroxy-D-proline. The structures suggest that the 10-fold greater preference for the L-stereoisomer is due to a serine residue that hydrogen bonds to the amine group of trans-4-hydroxy-L-proline. In contrast, the amine group of the D-stereoisomer lacks a direct interaction with the enzyme due to a different orientation of the pyrrolidine ring. These results suggest that hydroxyproline catabolism is subject to substrate inhibition by trans-4-hydroxy-L-proline, analogous to the known inhibition of proline catabolism by L-proline. Also, drugs targeting the first enzyme of hydroxyproline catabolism, by elevating the level of trans-4-hydroxy-L-proline, may inadvertently impair proline catabolism by the inhibition of ALDH4A1.

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