Partial Purification and Characterization of Soluble Isoform of Butyrylcholinesterase from Rat Intestine

Novel 6-alkyl-bridged 4-arylalkylpiperazin-1-yl derivatives of azepino[4,3-b]indol-1(2H)-one as potent BChE-selective inhibitors showing protective effects against neurodegenerative insults

Due to the putative role of butyrylcholinesterase (BChE) in regulation of acetylcholine levels and functions in the late stages of the Alzheimer's disease (AD), the potential of selective inhibitors (BChEIs) has been envisaged as an alternative to administration of acetylcholinesterase inhibitors (AChEIs). Starting from our recent findings, herein the synthesis and in vitro evaluation of cholinesterase (ChE) inhibition of a novel series of some twenty 3,4,5,6-tetrahydroazepino[4,3-b]indol-1(2H)-one derivatives, bearing at the indole nitrogen diverse alkyl-bridged 4-arylalkylpiperazin-1-yl chains, are reported. The length of the spacers, as well as the type of arylalkyl group affected the enzyme inhibition potency and BChE/AChE selectivity. Two compounds, namely 14c (IC50 = 163 nM) and 14d (IC50 = 65 nM), bearing at the nitrogen atom in position 6 a n-pentyl- or n-heptyl-bridged 4-phenethylpiperazin-1-yl chains, respectively, proved to be highly potent mixed-type inhibitors of both equine and human BChE isoforms, showing more than two order magnitude of selectivity over AChE. The study of binding kinetics through surface plasmon resonance (SPR) highlighted differences in their BChE residence times (8 and 47 s for 14c and 14d, respectively). Moreover, 14c and 14d proved to hit other mechanisms known to trigger neurodegeneration underlying AD and other CNS disorders. Unlike 14c, compound 14d proved also capable of inhibiting by more than 60% the in vitro self-induced aggregation of neurotoxic amyloid-β (Aβ) peptide at 100 μM concentration. On the other hand, 14c was slightly better than 14d in counteracting, at 1 and 10 μM concentration, glutamate excitotoxicity, due to over-excitation of NMDA receptors, and hydrogen peroxide-induced oxidative stress assessed in neuroblastoma cell line SH-SY5Y. This paper is dedicated to Prof. Marcello Ferappi, former dean of the Faculty of Pharmacy of the University of Bari, in the occasion of his 90th birthday.

Butyrylcholinesterase in lipid metabolism: A new outlook

Cholinesterase enzymes acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) are traditionally associated with the termination of acetylcholine mediated neural signaling. The fact that these ubiquitous enzymes are also found in tissues not involved in neurotransmission has led to search for alternative functions for these enzymes. Cholinesterases are reported to be involved in many lipid related disease states. Taking into view that lipases and cholinesterases belong to the same enzyme class and by comparing the catalytic sites, we propose a new outlook on the link between BChE and lipid metabolism. The lipogenic substrates of BChE that have recently emerged in contrast to traditional cholinesterase substrates are explained through the hydrolytic capacity of BChE for ghrelin, 4-methyumbelliferyl (4-mu) palmitate, and arachidonoylcholine and through endogenous lipid mediators such as cannabinoids like anandamide and essential fatty acids. The abundance of BChE in brain, intestine, liver, and plasma, tissues with active lipid metabolism, supports the idea that BChE may be involved in lipid hydrolysis. BChE is also regulated by various lipids such as linoleic acid, alpha-linolenic acid or dioctanoylglycerol, whereas AChE is inhibited. The finding that BChE is able to hydrolyze 4-mu palmitate at a pH where lipases are less efficient points to its role as a backup in lipolysis. In diseases such as Alzheimer, in which elevated BChE and impaired lipid levels are observed, the lipolytic activity of BChE might be involved. It is possible to suggest that fatty acids such as 4-mu palmitate, ghrelin, arachidonoylcholine, essential fatty acids, and other related lipid mediators regulate cholinesterases, which could lead to some sort of compensatory mechanism at high lipid concentrations.

Butyrylcholinesterase and lipid metabolism: Possible dual role in metabolic disorders

Butyrylcholinesterase (BChE), an enzyme primarily found in the liver, plasma, and brain, has been recognized for its role in the hydrolysis of choline esters. Recent studies have shed light on its involvement in lipid metabolism, revealing its potential as a crucial player in maintaining lipid homeostasis. However, the interactions between external factors and BChE activity in lipid metabolic pathways remain a complex subject of study. This review summarizes the current knowledge regarding BChE activity and lipid metabolism and seeks to clarify the nature of this relationship as causal or consequential. Evidence supports the role of BChE in energy homeostasis disruption, such as obesity and related metabolic disorders, where it exhibits lipolytic activity and mediates fatty acid use and storage. The unexpected functions of BChE in lipoprotein synthesis and the impact of polymorphic variants of the BCHE gene suggest a central role in lipid metabolism; however, further investigation is needed to confirm and describe these functions, especially considering the metabolic context. Furthermore, exploring therapeutic interventions in lipid metabolism disorders contributes to elucidating their implications on BChE activity, but attention to the metabolic status and genotypes as possible factors in this interaction is needed. In summary, further research in this field holds promise for improving our understanding of the complex interplay between BChE and lipid metabolism, and its potential clinical applications. However, the available data corroborate the dual role of BChE activity, both as a critical responsive element to metabolic challenges and as a predisposition factor to metabolic diseases.

Novel activity of human BChE: Lipid hydrolysis

Acetylcholinesterase and butyrylcholinesterase (BChE) typically hydrolyze the neurotransmitter acetylcholine. The multifunctional enzyme BChE is associated with lipid metabolism through an undefined mechanism. Based on lipid-related studies and by comparing the structural similarities between lipases and BChE we postulated that the association of BChE with lipid metabolism could occur through hydrolytic activity. Utilizing purified BChE enzymes from different sources and several lipases as controls, the ability of BChE to hydrolyze 4-methylumbelliferyl (4-mu) palmitate is investigated. Using lectin affinity, inhibition kinetics, and molecular modeling, we demonstrated that purified BChE hydrolyzed 4-mu palmitate at pH 8 as effectively as wheat germ lipase. The affinity K_m value of the enzymes for 4-mu palmitate as substrate is found as 10.4 μM, 34.2 μM, 129.8 μM, and 186 μM for wheat germ lipase, purified BChE, pancreatic lipase, and commercial BChE, respectively. Analysis of the inhibitory effect of 4-mu palmitate on BChE using butyrylthiocholine as substrate revealed competitive inhibition with K_i and IC₅₀ values of 448 μM and 987.2 μM, respectively. The binding affinity and interactions of 4-mu palmitate with BChE and pancreatic lipase were predicted by molecular docking. These results suggest that BChE possesses lipolytic activity. The possibility that BChE hydrolyzes not only 4-mu palmitate but also other types of lipids will lead to a new approach to those disease states associated with increased BChE activity/expression.

Purification and Kinetic Properties of 6-Phosphogluconate Dehydrogenase from Rat Small Intestine

6-Phosphogluconate dehydrogenase (6PG) was purified from rat small intestine with 36% yield and a specific activity of 15 U/mg. On SDS/PAGE, one band with a mass of 52 kDa was found. On native PAGE three protein and two activity bands were observed. The pH optimum was 7.35. Using Arrhenius plots, Ea, DeltaH, Q10 and Tm for 6PGD were found to be 7.52 kcal/mol, 6.90 kcal/mol, 1.49 and 49.4 degrees C, respectively. The enzyme obeyed "Rapid Equilibrium Random Bi Bi" kinetic model with Km values of 595 +/- 213 microM for 6PG and 53.03+/-1.99 microM for NADP. 1/Vm versus 1/6PG and 1/NADP plots gave a Vm value of 8.91+/-1.92 U/mg protein. NADPH is the competitive inhibitor with a Ki of 31.91+/-1.31 microM. The relatively small Ki for the 6PGD:NADPH complex indicates the importance of NADPH in the regulation of the pentose phosphate pathway through G6PD and 6PGD.