Carbonic anhydrase, its inhibitors and vascular function

It has been known for some time that Carbonic Anhydrase (CA, EC 4.2.1.1) plays a complex role in vascular function, and in the regulation of vascular tone. Clinically employed CA inhibitors (CAIs) are used primarily to lower intraocular pressure in glaucoma, and also to affect retinal blood flow and oxygen saturation. CAIs have been shown to dilate vessels and increase blood flow in both the cerebral and ocular vasculature. Similar effects of CAIs on vascular function have been observed in the liver, brain and kidney, while vessels in abdominal muscle and the stomach are unaffected. Most of the studies on the vascular effects of CAIs have been focused on the cerebral and ocular vasculatures, and in particular the retinal vasculature, where vasodilation of its vessels, after intravenous infusion of sulfonamide-based CAIs can be easily observed and measured from the fundus of the eye. The mechanism by which CAIs exert their effects on the vasculature is still unclear, but the classic sulfonamide-based inhibitors have been found to directly dilate isolated vessel segments when applied to the extracellular fluid. Modification of the structure of CAI compounds affects their efficacy and potency as vasodilators. CAIs of the coumarin type, which generally are less effective in inhibiting the catalytically dominant isoform hCA II and unable to accept NO, have comparable vasodilatory effects as the primary sulfonamides on pre-contracted retinal arteriolar vessel segments, providing insights into which CA isoforms are involved. Alterations of the lipophilicity of CAI compounds affect their potency as vasodilators, and CAIs that are membrane impermeant do not act as vasodilators of isolated vessel segments. Experiments with CAIs, that shed light on the role of CA in the regulation of vascular tone of vessels, will be discussed in this review. The role of CA in vascular function will be discussed, with specific emphasis on findings with the effects of CA inhibitors (CAI).

In-Silico Modeling in Drug Metabolism and Interaction: Current Strategies of Lead Discovery

BACKGROUND

Drug metabolism is a complex mechanism of human body systems to detoxify foreign particles, chemicals, and drugs through bio alterations. It involves many biochemical reactions carried out by invivo enzyme systems present in the liver, kidney, intestine, lungs, and plasma. After drug administration, it crosses several biological membranes to reach into the target site for binding and produces the therapeutic response. After that, it may undergo detoxification and excretion to get rid of the biological systems. Most of the drugs and its metabolites are excreted through kidney via urination. Some drugs and their metabolites enter into intestinal mucosa and excrete through feces. Few of the drugs enter into hepatic circulation where they go into the intestinal tract. The drug leaves the liver via the bile duct and is excreted through feces. Therefore, the study of total methodology of drug biotransformation and interactions with various targets is costly.

METHODS

To minimize time and cost, in-silico algorithms have been utilized for lead-like drug discovery. Insilico modeling is the process where a computer model with a suitable algorithm is developed to perform a controlled experiment. It involves the combination of both in-vivo and in-vitro experimentation with virtual trials, eliminating the non-significant variables from a large number of variable parameters. Whereas, the major challenge for the experimenter is the selection and validation of the preferred model, as well as precise simulation in real physiological status.

RESULTS

The present review discussed the application of in-silico models to predict absorption, distribution, metabolism, and excretion (ADME) properties of drug molecules and also access the net rate of metabolism of a compound.

CONCLUSION

It helps with the identification of enzyme isoforms; which are likely to metabolize a compound, as well as the concentration dependence of metabolism and the identification of expected metabolites. In terms of drug-drug interactions (DDIs), models have been described for the inhibition of metabolism of one compound by another, and for the compound-dependent induction of drug-metabolizing enzymes.

Codeinone reductase isoforms with differential stability, efficiency and product selectivity in opium poppy

Codeinone reductase (COR) catalyzes the reversible NADPH-dependent reduction of codeinone to codeine as the penultimate step of morphine biosynthesis in opium poppy (Papaver somniferum). It also irreversibly reduces neopinone, which forms by spontaneous isomerization in aqueous solution from codeinone, to neopine. In a parallel pathway involving 3-O-demethylated analogs, COR converts morphinone to morphine, and neomorphinone to neomorphine. Similar to neopine, the formation of neomorphine by COR is irreversible. Neopine is a minor substrate for codeine O-demethylase (CODM), yielding morphine. In the plant, neopine levels are low and neomorphine has not been detected. Silencing of CODM leads to accumulation of upstream metabolites, such as codeine and thebaine, but does not result in a shift towards higher relative concentrations of neopine, suggesting a mechanism in the plant for limiting neopine production. In yeast (Saccharomyces cerevisiae) engineered to produce opiate alkaloids, the catalytic properties of COR lead to accumulation of neopine and neomorphine as major products. An isoform (COR-B) was isolated from opium poppy chemotype Bea's Choice that showed higher catalytic activity than previously characterized CORs, and it yielded mostly neopine in vitro and in engineered yeast. Five catalytically distinct COR isoforms (COR1.1-1.4 and COR-B) were used to determine sequence-function relationships that influence product selectivity. Biochemical characterization and site-directed mutagenesis of native COR isoforms identified four residues (V25, K41, F129 and W279) that affected protein stability, reaction velocity, and product selectivity and output. Improvement of COR performance coupled with an ability to guide pathway flux is necessary to facilitate commercial production of opiate alkaloids in engineered microorganisms.

Response of α-glucosidase in gypsy moth larvae to acute and chronic dietary cadmium

We investigated the effects of acute and chronic treatments with cadmium at 10 μg Cd/g dry food and 30 μg Cd/g dry food on α-glucosidase activity of the 4th instar larvae of Lymantria dispar (Lepidoptera: Lymantriidae) as well as subsequent recovery. Enzyme inhibition was recorded during acute exposure to 30 μg Cd/g dry food and during chronic treatment at the lower metal concentration. After three days recovery from 10 μg Cd/g dry food, the α-glucosidase activity returned to the control level. One-way ANOVA showed that cadmium significantly influenced the activity of α-glucosidase during all treatments. The index of phenotypic plasticity was higher during chronic treatment at 10 μg Cd/g dry food than at 30 μg Cd/g as well as during the recovery. We detected four glucosidase isoforms by NATIVE PAGE. The activities and expressions of the isoforms depended on both larval genotype and cadmium treatment.