Molecular changes during the titration of α-keto-δ-aminovaleric acid

Cabello, J; Leon, B.; Prajoux, Victoria; Plaza, María Isabel Cornejo

doi:10.1016/0003-9861(64)90267-x

Cited by 24 publications

(12 citation statements)

References 16 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…One factor that may influence the reactions and equilibrium in the escapin/l-lysine pathway in vivo is pH, since the pH of sea hare ink is % 5 when secreted and % 8 when diluted in sea water, [27] and since pH is known to affect some reactions in the general LAAO pathway in vitro. [24,28] This issue of identifying molecular species in an equilibrium mixture, quantifying their relative abundances, and determining their bioactivity has analogs in other fields, such as in food sciences, where sugars exist as an equilibrium mixture and identifying the molecular species responsible for sweetness is important in product development. [29] The specific aims of this study were threefold.…”

mentioning

confidence: 99%

The Chemistry of Escapin: Identification and Quantification of the Components in the Complex Mixture Generated by an L‐Amino Acid Oxidase in the Defensive Secretion of the Sea Snail Aplysia californica

Kamio

Zheng

et al. 2009

Chemistry A European J

View full text Add to dashboard Cite

Escapin is an L-amino acid oxidase in the ink of a marine snail, the sea hare Aplysia californica, which oxidizes L-lysine (1) to produce a mixture of chemicals which is antipredatory and antimicrobial. The goal of our study was to determine the identity and relative abundance of the constituents of this mixture, using molecules generated enzymatically with escapin and also using products of organic syntheses. We examined this mixture under the natural range of pH values for ink-from approximately 5 at full strength to approximately 8 when fully diluted in sea water. The enzymatic reaction likely forms an equilibrium mixture containing the linear form alpha-keto-epsilon-aminocaproic acid (2), the cyclic imine Delta(1)-piperidine-2-carboxylic acid (3), the cyclic enamine Delta(2)-piperidine-2-carboxylic acid (4), possibly the linear enol 6-amino-2-hydroxy-hex-2-enoic acid (7), the alpha-dihydroxy acid 6-amino-2,2-dihydroxy-hexanoic acid (8), and the cyclic aminol 2-hydroxy-piperidine-2-carboxylic acid (9). Using NMR and mass spectroscopy, we show that 3 is the major component of this enzymatic product at any pH, but at more basic conditions, the equilibrium shifts to produce relatively more 4, and at acidic conditions, the equilibrium shifts to produce relatively more 2, 7, and/or 9. Studies of escapin's enzyme kinetics demonstrate that because of the high concentrations of escapin and L-lysine in the ink secretion, millimolar concentrations of 3, H(2)O(2), and ammonia are produced, and also lower concentrations of 2, 4, 7, and 9 as a result. We also show that reactions of this mixture with H(2)O(2) produce delta-aminovaleric acid (5) and delta-valerolactam (6), with 6 being the dominant component under the naturally acidic conditions of ink. Thus, the product of escapin's action on L-lysine contains an equilibrium mixture that is more complex than previously known for any L-amino acid oxidase.

show abstract

mentioning

confidence: 99%

The Chemistry of Escapin: Identification and Quantification of the Components in the Complex Mixture Generated by an L‐Amino Acid Oxidase in the Defensive Secretion of the Sea Snail Aplysia californica

Kamio

Zheng

et al. 2009

Chemistry A European J

View full text Add to dashboard Cite

show abstract

“…Therefore, the pK a of the substrate imine nitrogen should be related to EC, as was observed (Table 1). Human recombinant ketimine reductase/CRYM exhibits lower CE with T2C (the sulfur-containing analogue of Pyr2C) at neutral pH compared to Pyr2C (Table 2) despite the fact that they both exist only as ketimines at this pH [19,23]. Resonance stabilization by the sulfur atom of T2C may be the reason for this difference, resulting in a more stable molecule resistant to reduction and protonation.…”

Section: Substrate Specificitymentioning

confidence: 94%

“…We therefore suggest that ketimine reductase/CRYM may best be described as a P2C/Pyr2C reductase and that at neutral pH AECK is a poor substrate. The differences in CE were found to be directly related to the pK a values of the imine nitrogen (where known); pK a of P2C is 8.1 (CE 33.9 9 10 4 M -1 s -1 ) [37]), pK a of Pyr2C is 5.99 (CE 14.8 9 10 4 M -1 s -1 ) [19], whereas the pK a of T2C is 3.84 (CE 8.0 9 10 4 M -1 s -1 ) [23]. The ability of the imine nitrogen to accept a proton increases with increasing pK a value.…”

Section: Substrate Specificitymentioning

confidence: 96%

“…However, at neutral pH Pyr2C, P2C, and T2C exist predominantly as the enzymatically favorable cyclic ketimine form (in which the ring double bond is in the C=N form) [16,19,20] (Figs. 1, 2).…”

Section: L-thyroxinementioning

confidence: 99%

“…The activity with LK as a substrate was too low to perform reliable kinetic assays. All assays were performed with fixed concentrations of NADPH cofactor, namely 8 lM, and as such the kinetic constants are apparent constants a [38], b [19], c [23] (Table 1). A combination of resonance stabilization as well as hydrogen bonding between the amine and carboxylate group may also contribute to stabilize the enamine.…”

Section: Substrate Specificitymentioning

confidence: 99%

See 2 more Smart Citations

Insights into Enzyme Catalysis and Thyroid Hormone Regulation of Cerebral Ketimine Reductase/μ-Crystallin Under Physiological Conditions

et al. 2015

View full text Add to dashboard Cite

Mammalian ketimine reductase is identical to μ-crystallin (CRYM)-a protein that is also an important thyroid hormone binding protein. This dual functionality implies a role for thyroid hormones in ketimine reductase regulation and also a reciprocal role for enzyme catalysis in thyroid hormone bioavailability. In this research we demonstrate potent sub-nanomolar inhibition of enzyme catalysis at neutral pH by the thyroid hormones L-thyroxine and 3,5,3'-triiodothyronine, whereas other thyroid hormone analogues were shown to be far weaker inhibitors. We also investigated (a) enzyme inhibition by the substrate analogues pyrrole-2-carboxylate, 4,5-dibromopyrrole-2-carboxylate and picolinate, and (b) enzyme catalysis at neutral pH of the cyclic ketimines S-(2-aminoethyl)-L-cysteine ketimine (owing to the complex nomenclature trivial names are used for the sulfur-containing cyclic ketimines as per the original authors' descriptions) (AECK), Δ(1)-piperideine-2-carboxylate (P2C), Δ(1)-pyrroline-2-carboxylate (Pyr2C) and Δ(2)-thiazoline-2-carboxylate. Kinetic data obtained at neutral pH suggests that ketimine reductase/CRYM plays a major role as a P2C/Pyr2C reductase and that AECK is not a major substrate at this pH. Thus, ketimine reductase is a key enzyme in the pipecolate pathway, which is the main lysine degradation pathway in the brain. In silico docking of various ligands into the active site of the X-ray structure of the enzyme suggests an unusual catalytic mechanism involving an arginine residue as a proton donor. Given the critical importance of thyroid hormones in brain function this research further expands on our knowledge of the connection between amino acid metabolism and regulation of thyroid hormone levels.

show abstract

Kynureninases: Enzymological Properties and Regulation Mechanism

Soda¹,

Tanizawa²

1979

Advances in Enzymology - And Related Areas of Molecular Biology

View full text Add to dashboard Cite

Molecular changes during the titration of α-keto-δ-aminovaleric acid

Cited by 24 publications

References 16 publications

The Chemistry of Escapin: Identification and Quantification of the Components in the Complex Mixture Generated by an L‐Amino Acid Oxidase in the Defensive Secretion of the Sea Snail Aplysia californica

The Chemistry of Escapin: Identification and Quantification of the Components in the Complex Mixture Generated by an L‐Amino Acid Oxidase in the Defensive Secretion of the Sea Snail Aplysia californica

Insights into Enzyme Catalysis and Thyroid Hormone Regulation of Cerebral Ketimine Reductase/μ-Crystallin Under Physiological Conditions

Kynureninases: Enzymological Properties and Regulation Mechanism

Contact Info

Product

Resources

About