Significance of Protein–Substrate Hydrogen Bonding for the Selectivity of P450‐Catalysed Oxidations

Synthesis of substituted norcaranes for use as probes of enzyme mechanisms

Norcarane is a mechanistic probe of monooxygenase enzymes that is able to detect the presence of cationic or radical intermediates. The addition of substituents around the bicycloheptane ring of the norcarane scaffold can assist in improving enzyme binding affinity and thus improve the regioselectivity of oxidation. Here we prepare in three-step, diastereoselective syntheses, ten norcaranes monosubstituted α to the cyclopropane as advanced probes. Four of these compounds were examined in enzyme binding experiments to evaluate their potential as probe substrates. Additionally, 19 potential products of enzymatic oxidation were generated via two additional synthetic steps for use as product standards in future studies.

From random to rational: improving enzyme design through electric fields, second coordination sphere interactions, and conformational dynamics

Enzymes are versatile and efficient biological catalysts that drive numerous cellular processes, motivating the development of enzyme design approaches to tailor catalysts for diverse applications. In this perspective, we investigate the unique properties of natural, evolved, and designed enzymes, recognizing their strengths and shortcomings. We highlight the challenges and limitations of current enzyme design protocols, with a particular focus on their limited consideration of long-range electrostatic and dynamic effects. We then delve deeper into the impact of the protein environment on enzyme catalysis and explore the roles of preorganized electric fields, second coordination sphere interactions, and protein dynamics for enzyme function. Furthermore, we present several case studies illustrating successful enzyme-design efforts incorporating enzyme strategies mentioned above to achieve improved catalytic properties. Finally, we envision the future of enzyme design research, spotlighting the challenges yet to be overcome and the synergy of intrinsic electric fields, second coordination sphere interactions, and conformational dynamics to push the state-of-the-art boundaries.

Melatonin Activation by Human Cytochrome P450 Enzymes: A Comparison between Different Isozymes

Cytochrome P450 enzymes in the human body play a pivotal role in both the biosynthesis and the degradation of the hormone melatonin. Melatonin plays a key role in circadian rhythms in the body, but its concentration is also linked to mood fluctuations as well as emotional well-being. In the present study, we present a computational analysis of the binding and activation of melatonin by various P450 isozymes that are known to yield different products and product distributions. In particular, the P450 isozymes 1A1, 1A2, and 1B1 generally react with melatonin to provide dominant aromatic hydroxylation at the C6-position, whereas the P450 2C19 isozyme mostly provides O-demethylation products. To gain insight into the origin of these product distributions of the P450 isozymes, we performed a comprehensive computational study of P450 2C19 isozymes and compared our work with previous studies on alternative isozymes. The work covers molecular mechanics, molecular dynamics and quantum mechanics approaches. Our work highlights major differences in the size and shape of the substrate binding pocket amongst the different P450 isozymes. Consequently, substrate binding and positioning in the active site varies substantially within the P450 isozymes. Thus, in P450 2C19, the substrate is oriented with its methoxy group pointing towards the heme, and therefore reacts favorably through hydrogen atom abstraction, leading to the production of O-demethylation products. On the other hand, the substrate-binding pockets in P450 1A1, 1A2, and 1B1 are tighter, direct the methoxy group away from the heme, and consequently activate an alternative site and lead to aromatic hydroxylation instead.

Emerging Metabolic Profiles of Sulfonamide Antibiotics by Cytochromes P450: A Computational-Experimental Synergy Study on Emerging Pollutants

Metabolism, especially by CYP450 enzymes, is the main reason for mediating the toxification and detoxification of xenobiotics in humans, while some uncommon metabolic pathways, especially for emerging pollutants, probably causing idiosyncratic toxicity are easily overlooked. The pollution of sulfonamide antibiotics in aqueous system has attracted increasing public attention. Hydroxylation of the central amine group can trigger a series of metabolic processes of sulfonamide antibiotics in humans; however, this work parallelly reported the coupling and fragmenting initiated by amino H-abstraction of sulfamethoxazole (SMX) catalyzed by human CYP450 enzymes. Elucidation of the emerging metabolic profiles was mapped via a multistep synergy between computations and experiments, involving preliminary DFT computations and in vitro and in vivo assays, profiling adverse effects, and rationalizing the fundamental factors via targeted computations. Especially, the confirmed SMX dimer was shown to potentially act as a metabolism disruptor in humans, while spin aromatic delocalization resulting in the low electron donor ability of amino radicals was revealed as the fundamental factor to enable coupling of sulfonamide antibiotics by CYP450 through the nonconventional nonrebound pathway. This work may further strengthen the synergistic use of computations prior to experiments to avoid wasteful experimental screening efforts in environmental chemistry and toxicology.

Insights into the binding mechanism between α-TOH and CYP4F2: A homology modeling, molecular docking, and molecular dynamics simulation study

α-Tocopherol (α-TOH) is a potent antioxidant. The concentrations of α-TOH in plasma are closely related to human health. α-TOH can be regulated by the metabolism of cytochrome P450 4F2 (CYP4F2). However, the atomic-level basis for this regulation process remains elusive. Here, we successfully constructed the structure of CYP4F2 by homology modeling and obtained the α-TOH-CYP4F2 complex models using molecular docking. Three parallel 500 ns molecular dynamics simulations were performed on each complex model to investigate the details of the interaction between α-TOH and CYP4F2. MM-GBSA method combined with principal component analysis shows that 8 key residues establish a hydrophobic cavity stabilizing α-TOH in the pocket of CYP4F2 and S423 forms an important hydrogen bond with α-TOH anchoring α-TOH in the favorable position for ω-hydroxylation. Based on our simulation results and the experimental facts, we designed mutation simulation experiments to clarify the important role of two key residues (S423 and V433) in the binding of α-TOH with CYP4F2. The results show that the mutations directly or indirectly change the binding mode of α-TOH and decrease its binding affinity with CYP4F2, which is unfavorable for ω-hydroxylation. Our results could enrich the information on structure-function relationships of CYP4F2 and provide valuable insights into the regulatory mechanism of CYP4F2 on the metabolism of α-TOH.

Can Eucalyptol Replace Antibiotics?

One of the primary reasons for the search for new antimicrobial agents is the increasing and spreading resistance of microorganisms to previously used drugs. This is particularly important in the case of rapidly progressing infections that require the rapid administration of an appropriately selected antibiotic. However, along with the administration of antibiotics, complications in the disease-weakened body may arise in the form of systemic mycoses, viral infections, and protozoan infections. Therefore, there is an increasing interest among researchers focusing on the use of naturally occurring terpenic compounds in stand-alone or combined therapies with antibiotics. In this publication, the aim of our work is to present the results of a literature review on the antimicrobial activity of eucalyptol.

Proton relay network in P450cam formed upon docking of putidaredoxin

Cytochromes P450 are versatile heme-based enzymes responsible for vital life processes. Of these, P450cam (substrate camphor) has been most studied. Despite this, precise mechanisms of the key O─O cleavage step remain partly elusive to date; effects observed in various enzyme mutants remain partly unexplained. We have carried out extended (to 1000 ns) MM-MD and follow-on quantum mechanics/molecular mechanics computations, both on the well-studied FeOO state and on Cpd(0) (compound 0). Our simulations include (all camphor-bound): (a) WT (wild type), FeOO state. (b) WT, Cpd(0). (c) Pdx (Putidaredoxin, redox partner of P450)-docked-WT, FeOO state. (d) Pdx-docked WT, Cpd(0). (e) Pdx-docked T252A mutant, Cpd(0). Among our key findings: (a) Effect of Pdx docking appears to go far beyond that indicated in prior studies: it leads to specific alterations in secondary structure that create the crucial proton relay network. (b) Specific proton relay networks we identify are: FeOO(H)⋯T252⋯nH ₂ O⋯D251 in WT; FeOO(H)⋯nH ₂ O⋯D251 in T252A mutant; both occur with Pdx docking. (c) Direct interaction of D251 with -FeOOH is, respectively, rare/frequent in WT/T252A mutant. (d) In WT, T252 is in the proton relay network. (e) Positioning of camphor appears significant: when camphor is part of H-bonding network, second protonation appears to be facilitated.