Structure−Activity Studies of l-Canaline-Mediated Inhibition of Porcine Alanine Aminotransferase

Abstract

L-Canaline [L-2-amino-4-(aminooxy)butanoic acid] (L-CAN) and a family of eleven structurally related analogs were synthesized and evaluated for their inhibitory effect on PLP-dependent alanine aminotransferase (AlaAT) (EC 2.6.1.2) obtained from porcine heart. These congeners were selected to determine the stereochemical, aliphatic chain length, and aminooxy substitutional effects on L-CAN-mediated inhibition of AlaAT activity. L-CAN was the most effective inhibitor of the tested compounds; 10(-7) M L-CAN elicited a 55% reduction in AlaAT activity after a 5 min exposure. This deleterious effect results from the ability of L-CAN to react avidly with PLP moiety of the enzyme to form a stable, L-CAN-PLP oxime. In contrast, the methyl and ethyl esters of L-CAN reduced AlaAT activity by only 8% and 6%, respectively. While all of the L-enantiomeric forms of the tested compound were more potent AlaAT inhibitors than their corresponding D-stereoisomers, the D-enantiomers, particularly D-canaline, were active. Chain shortening or lengthening dramatically curtailed L-CAN-mediated loss in AlaAT activity, but the replacement of the alpha-amino group with a hydrogen was of little consequence in this regard. AlaAT was treated with L-CAN in the presence of free PLP to assess PLP capacity to protect AlaAT against 10(7) M L-CAN-dependent inactivation. L-CAN retained approximately two-thirds of its inhibitory ability in the presence of equimolar PLP, but AlaAT inhibition was reduced 90% by a 10-fold excess of PLP over L-CAN.

Ornithine Aminotransferase versus GABA Aminotransferase: Implications for the Design of New Anticancer Drugs

“…In fact, AFPA, L-canaline, and aminooxypropionic acid are fairly nonselective. 49,60 The binding pockets of OAT and GABA-AT are similar as well, as noted earlier. One of the main reasons why many molecules can bind to both enzymes indiscriminately is the fact that the Figure 11.…”

“…These reactive groups, however, are not expected to have a great impact on enzyme selectivity. In fact, AFPA, l ‐canaline, and aminooxypropionic acid are fairly nonselective …”

Branched-chain amino acid aminotransferase and methionine formation in Mycobacterium tuberculosis

“…These four inhibitors and canaline, an aminooxy analogue of ornithine that has been demonstrated to be an effective aminotransferase inhibitor in other systems [16,17,26-28], were screened against M. tuberculosis and M. marinum in vitro to determine potential antimicrobial activity. M. marinum is a close relative of M. tuberculosis that causes a similar disease in fish, grows faster than M. tuberculosis in culture, and does not cause serious infections in humans [29].…”

The Mechanism of l-Canavanine Cytotoxicity: Arginyl tRNA Synthetase as a Novel Target for Anticancer Drug Discovery

“…L-canaline, is formed when arginase hydrolyzes the oxyguanidino group of L-canavanine, generating the oxygen isostere of L-ornithine, as illustrated in Figure 9. 69 Although L-canaline is an inhibitor of pyridoxal phosphate (PLP)-dependent enzymes and has cytotoxic properties, 65,70,71 the in vitro growth inhibitory effects of L-canavanine in the pancreatic cell line MIA PaCa-2 do not appear to be attributable to the conversion of L-canavanine to L-canaline. 72 The contribution of L-canaline to the in vivo cytotoxicity of L-canavanine has not yet been determined.…”