| Structural highlights
Disease
[OAT_HUMAN] Defects in OAT are the cause of hyperornithinemia with gyrate atrophy of choroid and retina (HOGA) [MIM:258870]. HOGA is a slowly progressive blinding autosomal recessive disorder.[1] [2] [3] [4] [5] [6]
Publication Abstract from PubMed
Potent mechanism-based inactivators can be rationally designed against PLP-dependent drug targets, such as ornithine aminotransferase (OAT) or gamma-aminobutyric acid aminotransferase (GABA-AT). An important challenge, however, is the lack of selectivity towards other PLP-dependent off-target enzymes, because of similarities in mechanisms of all PLP-dependent aminotransferase reactions. On the basis of complex crystal structures, we investigate the inactivation mechanism of OAT, a hepatocellular carcinoma (HCC) target, by (1R,3S,4S)-3-amino-4-fluorocyclopentane-1-carboxylic acid (FCP), a known inactivator of GABA-AT. A crystal structure of OAT and FCP showed the formation of a ternary adduct. This adduct can be rationalized as occurring via an enamine mechanism of inactivation similar to that reported for GABA-AT. However, the crystal structure of an off-target PLP-dependent enzyme, aspartate aminotransferase (Asp-AT), in complex with FCP, along with the results of attempted inhibition assays, suggest that FCP is not an inactivator of Asp-AT, but rather an alternate substrate. Turnover of FCP by Asp-AT is also supported by high-resolution mass spectrometry. In comparison to the inactivation mechanisms of FCP against OAT and GABA-AT, the obtained results provide evidence that a desirable selectivity of inactivation could be achieved, taking advantage of subtle structural and mechanistic differences between a drug-target and an off-target enzyme, despite their largely similar substrate binding sites and catalytic mechanisms.
Selective Targeting by a Mechanism-based Inactivator against PLP-Dependent Enzymes: Mechanisms of Inactivation and Alternative Turnover.,Mascarenhas R, Le HV, Clevenger KD, Lehrer HJ, Ringe D, Kelleher NL, Silverman RB, Liu D Biochemistry. 2017 Aug 17. doi: 10.1021/acs.biochem.7b00499. PMID:28816437[7]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Ramesh V, McClatchey AI, Ramesh N, Benoit LA, Berson EL, Shih VE, Gusella JF. Molecular basis of ornithine aminotransferase deficiency in B-6-responsive and -nonresponsive forms of gyrate atrophy. Proc Natl Acad Sci U S A. 1988 Jun;85(11):3777-80. PMID:3375240
- ↑ Inana G, Chambers C, Hotta Y, Inouye L, Filpula D, Pulford S, Shiono T. Point mutation affecting processing of the ornithine aminotransferase precursor protein in gyrate atrophy. J Biol Chem. 1989 Oct 15;264(29):17432-6. PMID:2793865
- ↑ Michaud J, Brody LC, Steel G, Fontaine G, Martin LS, Valle D, Mitchell G. Strand-separating conformational polymorphism analysis: efficacy of detection of point mutations in the human ornithine delta-aminotransferase gene. Genomics. 1992 Jun;13(2):389-94. PMID:1612597
- ↑ Brody LC, Mitchell GA, Obie C, Michaud J, Steel G, Fontaine G, Robert MF, Sipila I, Kaiser-Kupfer M, Valle D. Ornithine delta-aminotransferase mutations in gyrate atrophy. Allelic heterogeneity and functional consequences. J Biol Chem. 1992 Feb 15;267(5):3302-7. PMID:1737786
- ↑ Michaud J, Thompson GN, Brody LC, Steel G, Obie C, Fontaine G, Schappert K, Keith CG, Valle D, Mitchell GA. Pyridoxine-responsive gyrate atrophy of the choroid and retina: clinical and biochemical correlates of the mutation A226V. Am J Hum Genet. 1995 Mar;56(3):616-22. PMID:7887415
- ↑ Kobayashi T, Ogawa H, Kasahara M, Shiozawa Z, Matsuzawa T. A single amino acid substitution within the mature sequence of ornithine aminotransferase obstructs mitochondrial entry of the precursor. Am J Hum Genet. 1995 Aug;57(2):284-91. PMID:7668253
- ↑ Mascarenhas R, Le HV, Clevenger KD, Lehrer HJ, Ringe D, Kelleher NL, Silverman RB, Liu D. Selective Targeting by a Mechanism-based Inactivator against PLP-Dependent Enzymes: Mechanisms of Inactivation and Alternative Turnover. Biochemistry. 2017 Aug 17. doi: 10.1021/acs.biochem.7b00499. PMID:28816437 doi:http://dx.doi.org/10.1021/acs.biochem.7b00499
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