| 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
The inhibition of ornithine aminotransferase (OAT), a pyridoxal 5'-phosphate-dependent enzyme, has been implicated as a treatment for hepatocellular carcinoma (HCC), the most common form of liver cancer, for which there is no effective treatment. From a previous evaluation of our aminotransferase inhibitors, (1S,3S)-3-amino-4-(perfluoropropan-2-ylidene)cyclopentane-1-carboxylic acid hydrochloride (1) was found to be a selective and potent inactivator of human OAT (hOAT), which inhibited the growth of HCC in athymic mice implanted with human-derived HCC, even at a dose of 0.1 mg/kg. Currently, investigational new drug (IND)-enabling studies with 1 are underway. The inactivation mechanism of 1, however, has proved to be elusive. Here we propose three possible mechanisms, based on mechanisms of known aminotransferase inactivators: Michael addition, enamine addition, and fluoride ion elimination followed by conjugate addition. On the basis of crystallography and intact protein mass spectrometry, it was determined that 1 inactivates hOAT through fluoride ion elimination to an activated 1,1'-difluoroolefin, followed by conjugate addition and hydrolysis. This result was confirmed with additional studies, including the detection of the cofactor structure by mass spectrometry and through the identification of turnover metabolites. On the basis of this inactivation mechanism and to provide further evidence for the mechanism, analogues of 1 (19, 20) were designed, synthesized, and demonstrated to have the predicted selective inactivation mechanism. These analogues highlight the importance of the trifluoromethyl group and provide a basis for future inactivator design.
Mechanism of Inactivation of Ornithine Aminotransferase by (1S,3S)-3-Amino-4-(hexafluoropropan-2-ylidenyl)cyclopentane-1-carboxylic Acid.,Moschitto MJ, Doubleday PF, Catlin DS, Kelleher NL, Liu D, Silverman RB J Am Chem Soc. 2019 Jul 10;141(27):10711-10721. doi: 10.1021/jacs.9b03254. Epub, 2019 Jun 28. PMID:31251613[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
- ↑ Moschitto MJ, Doubleday PF, Catlin DS, Kelleher NL, Liu D, Silverman RB. Mechanism of Inactivation of Ornithine Aminotransferase by (1S,3S)-3-Amino-4-(hexafluoropropan-2-ylidenyl)cyclopentane-1-carboxylic Acid. J Am Chem Soc. 2019 Jul 10;141(27):10711-10721. doi: 10.1021/jacs.9b03254. Epub, 2019 Jun 28. PMID:31251613 doi:http://dx.doi.org/10.1021/jacs.9b03254
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