4′-CyanoPLP presents better prospect for the experimental detection of elusive cyclic intermediate radical in the reaction of lysine 5,6-aminomutase

Maity, Amarendra Nath; Ke, Shyue-Chu

doi:10.1016/j.bbrc.2014.12.076

Cited by 4 publications

(3 citation statements)

References 22 publications

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“…Thus, the depth of the I • energy well offers a great prospect for experimental observation of the hitherto undetected I • . The degree of radical stabilization (10.3 kJ mol –1 , relative to S • ) obtained with PLP-NO is comparable with those with 4′-π-acceptor-PLPs using acetylenyl (7.9 kJ mol –1 ), cyano (9.4 kJ mol –1 ), or vinyl (18.9 kJ mol –1 ) substitution at the exocyclic 4′-carbon proposed earlier. The question of whether 5,6-LAM can tolerate PLP-NO as a cofactor is of great interest and is subjected to further investigation for its reaction with the enzyme.…”

Section: Resultssupporting

confidence: 82%

“…In the case of 5,6-LAM, the substrate-related radical was detected , using a substrate analog 4-thialysine and later unambiguously characterized using labeled 4-thialysines. − High-energy intermediate I • has been eluding experimental detection. DFT computations have been playing complementary roles in the research for radical aminomuatses. ,,− Radom and co-workers proposed analogs of PLP having substitution at the 4′-carbon with π acceptors, such as vinyl and acetylenyl are promising candidates for experimental observation of the corresponding I • . Moreover, our recent results predict that another π acceptor cyano substitution offers better prospect for the same purpose .…”

Section: Introductionmentioning

confidence: 99%

“…DFT computations have been playing complementary roles in the research for radical aminomuatses. ,,− Radom and co-workers proposed analogs of PLP having substitution at the 4′-carbon with π acceptors, such as vinyl and acetylenyl are promising candidates for experimental observation of the corresponding I • . Moreover, our recent results predict that another π acceptor cyano substitution offers better prospect for the same purpose . However, the acceptance of these analogs (4′-π-acceptor-PLPs) by 5,6-LAM is a matter of concern.…”

Section: Introductionmentioning

confidence: 99%

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Reaction of Pyridoxal-5′-phosphate-N-oxide with Lysine 5,6-Aminomutase: Enzyme Flexibility toward Cofactor Analog

et al. 2015

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Lysine 5,6-aminomutase (5,6-LAM) is a 5′-deoxyadenosylcobalamin and pyridoxal-5′-phosphate (PLP) codependent radical enzyme that can accept at least three substrates, d-lysine, l-β-lysine and l-lysine. The reaction of 5,6-LAM is believed to follow an intramolecular radical rearrangement mechanism involving formation of a cyclic azacyclopropylcarbinyl radical intermediate (I•). Similar I•s are also proposed for other radical aminomutases, such as ornithine 4,5-aminomutase (4,5-OAM) and lysine 2,3-aminomutase (2,3-LAM). Nevertheless, experimental proof in support of the participation of I• have been elusive. PLP is proposed to lower the energy of this elusive I• by captodative stabilization and spin delocalization. In this work, we employ PLP-N-oxide (PLP-NO) to investigate the flexibility of 5,6-LAM toward cofactor analog and participation of I• in the reaction mechanism. Our calculations show that substitution of PLP-NO for PLP stabilizes I• by 35.2 kJ mol–1 as a result of enhanced spin delocalization, which becomes the lowest energy state along the reaction sequence. Kinetic parameters and spectroscopic observations for PLP-NO similar to those of PLP demonstrate that PLP-NO mimics natural cofactor for 5,6-LAM. Interestingly, the flexibility of 5,6-LAM toward cofactor analog PLP-NO makes it an even more promising candidate for biocatalytic applications. Expectedly, the catalytic efficiency (k cat/K m) is reduced by ∼3 times with PLP-NO as a cofactor. Various factors, including higher stabilization of proposed corresponding I• for PLP-NO than that of PLP, could lead to the decrease in activity.

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Section: Resultssupporting

confidence: 82%