Catechol O-methyltransferase and indolethylamine N-methyltransferase activity in cerebrospinal fluid of dog, cat and human

Mining and Characterization of Indolethylamine N-Methyltransferases in Amphibian Toad Bufo gargarizans

Strong, psychedelic indolethylamines (IAAs) are typically present in trace amounts in the majority of species, but they build up significantly in the skin of amphibian toads, especially N-methylated 5-hydroxytryptamine (5-HT) analogues. However, there is no pertinent research on the investigation of indoleamine N-methyltransferase (INMT) in amphibians, nor is there any adequate information on the key amino acids that influence the activity of known INMTs from other species. Herein, we focused on Bufo toad INMT (BINMT) for the first time and preliminarily identified BINMT 1 from the transcriptomes of Bufo gargarizans active on tryptamine, 5-HT, and N-methyl-5-HT. We established the enzyme kinetic characteristics of BINMT 1 and identified the essential amino acids influencing its activity via molecular docking and site-directed mutagenesis. Subsequently, we carried out sequence alignment and phylogenetic tree analysis on 43 homologous proteins found in the genome of B. gargarizans with BINMT 1 as the probe and selected seven of them for protein expression and activity assays. It was found that only three proteins possessing the highest similarity to BINMT 1 had INMT activity. Our research unveils the binding residues of BINMT for 5-HT analogues for the first time and initiates the study of INMTs in amphibian toads, serving as a tentative reference for further study of BINMT and providing insight into the comprehension of BINMT's catalytic mechanism and its role in the biosynthesis of 5-HT analogues in Bufo toads. It also contributes to the expansion of the INMT library to help explore and explain interspecies evolution in the future.

Correlation between brain tissue and cerebrospinal fluid concentrations of selected compounds in rats with intact and injured blood-brain barrier

We examined how the concentrations of exogenous compounds (and their metabolites) in rat brain tissue correlate with their concentrations in the cerebrospinal fluid (CSF) (i) when the blood-brain barrier (B-BB) is intact and increasing doses of compounds are administered, and (ii) when the function of the B-BB is impaired and small constant doses are given. The impairment of B-BB function was caused by chlorophenoxyacetic acid herbicides. An excellent linear correlation between brain tissue and CSF concentrations, calculated from 14C activities, was obtained with 14C-p-aminobenzoic acid, 14C-antipyrine, and 14C-sucrose administered in increasing doses (to 320 mg/kg, i.v.) to B-BB-intact animals (r = 0.92 to 0.99, P less than 0.001). After the administration of small, constant, i.v. doses of 14C-methyl-4-chlorophenoxyacetic acid, 14C-2,4-dichlorophenoxyacetic acid, or 14C-p-aminobenzoic acid into B-BB-damaged rats, both brain tissue and CSF radioactivities increased about linearly 10-fold or more when the lesions progressed. A close correlation between brain tissue and CSF radioactivities was calculated with each compound (r = 0.97 to 0.99, P less than 0.001). In tests with small constant amounts of 14C-antipyrine, 14C-sucrose, and 125I-labeled human albumin, however, no marked linear correlation could be drawn. This was due to the fact that these compounds always caused roughly the same 14C activities both in the brain tissue and in CSF, i.e., their cerebral penetration was only slightly or negligibly affected by the B-BB impairment. The results suggest that significant changes in compound penetration into rat brain tissue can be monitored in the CSF.

[Purification and properties of rat kidney catechol-O-methyltransferase]

The S-adenosyl-methionine: catechol-O-methyltransferase (EC 2.1.1.6) from rat kidney was purified about 650 fold as compared with the homogenate and the result of disc electrophoresis presented. The purification involved extraction, precipitation at pH 5, ammonium sulfate fractionation, Chromatographies on Biogel 0.5 m, Ultrogel AcA 44 and DE Sephadex A 50. Affinity chromatography was tried but unsuccessful. The enzyme exhibited two pH optima at 7.9 and 9.6 with a minimum at about 8.9. The COMT had a temperature optimum of 50 degrees C, with activation energy of 23.1 Kcal/Mole between 25-35 degrees C, 18.9 Kcal/mole between 35-45 degrees C and the Q10 within the range of 25-35 degrees amounted to 3.5. The molecular weight was estimated to be 21500+/-1000 daltons from its behavior on Ultrogel AcA 44 and the pH1 determined by electrofocalisation was near 5.50. The time of half life of the best purified enzymatic extract was found to be 2 h 10 min. at -20 degrees C. At basic pH the instability of the enzyme was increased. Since O-methylation required the presence of divalent cations, our results show that apparent Michaelis constants for Mg++ and Mn++ were respectively 0.50 X 10(-3) M and 0.33 X 10(-5) M. The study of their Hill's number indicated that there was only one point of fixation on the enzyme. The Km value determined by Florini and Vestling's method were 2.5 X 10(-4) M and 11.9 X 10(-5) M for epinephrine and S-adenosyl-methionine respectively. All results were discussed with respect to other investigations.