Mode of Action of Herbicidal Derivatives of Aminomethylenebisphosphonic Acid. Part II. Reversal of Herbicidal Action by Aromatic Amino Acids

The herbicidal action of N-pyridylaminomethylenebisphosphonic acids is accompanied by an impairment of anthocyanin biosynthesis. This suggests that they might act as inhibitors of some steps in aromatic amino acid biosynthesis. Herbicidal effects were reversed by aromatic amino acids using both bacterial and plant models, a finding that strongly supports this hypothesis. Structural features of these compounds suggest the sixth enzyme in the shikimate pathway 5-enol-pyruvoylshikimate-3-phosphate (EPSP) synthase as a possible target, since a strong structural similarity exists between aminomethylenebisphosphonic acid and an inhibitor of EPSP synthase, the herbicide glyphosate. This is, however, not the case since they did not act as inhibitors of this enzyme. Received July 29; 1996; accepted May 27, 1997     

Enhanced transgenic plant resistance to nematodes by dual proteinase inhibitor constructs

Plant defence strategies usually involve the action of several gene products. Transgenic resistance strategies are likely to have enhanced efficacy when they involve more than one transgene. Here we explore possible mechanisms for the co-delivery of multiple effectors via a single transgene. As an example we report the co-delivery of two distinct proteinase inhibitors in Arabidopsis thaliana (L.) Heynh. to examine resistance against plant parasitic nematodes. A cysteine and serine proteinase inhibitor have been joined as translational fusions by one of two peptide linkers. One linker, part of the spacer region of a plant metallothionein-like protein (PsMTa), was selected to be cleaved in planta. A second linker, derived from the fungal enzyme galactose oxidase (GO) was chosen to be refractory to cleavage in planta. Western blot analysis of cell extracts confirmed the expected pattern of predominantly single inhibitors derived from the PsMTa construct and a primarily dual inhibitor from the GO construct. Analysis of cyst and root-knot nematodes recovered from transgenic Arabidopsis expressing inhibitors as single or dual molecules revealed the uptake of inhibitors with the exception of those linked by the PsMTa linker. This unexpected result may be due to residues of the PsMTa linker interacting with cell membranes. Despite lack of ingestion, PsMTa-linked cowpea trypsin inhibitor (CpTI) affected the sexual development of the cyst nematodes, indicating an external site of action. The engineered cystatin (Oc-IΔD86) component from the PsMTa constuct had no effect, indicating that ingestion is necessary for the cystatin to be effective. The delivery of dual inhibitors linked by the GO linker showed a clear additive effect over either inhibitor delivered singly. The application of this technology to other plant pathogens is discussed. Received: 3 July 1997 / Accepted: 8 August 1997     

Allopregnanolone induces state-dependent fear via the bed nucleus of the stria terminalis

Gonadal steroids and their metabolites have been shown to be important modulators of emotional behavior. Allopregnanolone (ALLO), for example, is a metabolite of progesterone that has been linked to anxiety-related disorders such as posttraumatic stress disorder. In rodents, it has been shown to reduce anxiety in a number of behavioral paradigms including Pavlovian fear conditioning. We have recently found that expression of conditioned contextual (but not auditory) freezing in rats can be suppressed by infusion of ALLO into the bed nucleus of the stria terminalis (BNST). To further explore the nature of this effect, we infused ALLO into the BNST of male rats prior to both conditioning and testing. We found that suppression of contextual fear occurred when the hormone was present during either conditioning or testing but not during both procedures, suggesting that ALLO acts in a state-dependent manner within the BNST. A shift in interoceptive context during testing for animals conditioned under ALLO provided further support for this mechanism of hormonal action on contextual fear. Interestingly, infusions of ALLO into the basolateral amygdala produced a state-independent suppression of both conditioned contextual and auditory freezing. Altogether, these results suggest that ALLO can influence the acquisition and expression of fear memories by both state-dependent and state-independent mechanisms.     

Kinetics of protein aggregation. Quantitative estimation of the chaperone-like activity in test-systems based on suppression of protein aggregation

The experimental data on the kinetics of irreversible aggregation of proteins caused by exposure to elevated temperatures or the action of denaturing agents (guanidine hydrochloride, urea) have been analyzed. It was shown that the terminal phase of aggregation followed, as a rule, first order kinetics. For the kinetic curves registered by an increase in the apparent absorbance (A) in time (t) the methods of estimation of the corresponding kinetic parameters A _lim and k _I (A _lim is the limiting value of A at t and k _I is the rate constant of the first order) have been proposed. Cases are revealed when the reaction rate constant k _I calculated from the kinetic curve of aggregation of the enzymes coincides with the rate constant for enzyme inactivation. Such a situation is interpreted as a case when the rate of aggregation is limited by the stage of denaturation of the enzyme. A conclusion has been made that, in order to establish the mechanism of protein aggregation, the kinetic investigations of aggregation should be carried out over a wide range of protein concentrations. The refolding experiments after denaturation of proteins by guanidine hydrochloride or urea have been also analyzed. It was shown that aggregation accompanying refolding follows first order kinetics at the final phase of the process. The model of protein refolding explaining such a kinetic regularity has been proposed. When aggregation of protein substrate follows first order kinetics, parameters A _lim and k _I may be used for the quantitative characterization of the chaperone-like activity in the test-systems based on suppression of protein aggregation.     

Biotechnological strategies to overcome inhibitors in lignocellulose hydrolysates for ethanol production: review

One of the major challenges faced in commercial production of lignocellulosic bioethanol is the inhibitory compounds generated during the thermo-chemical pre-treatment step of biomass. These inhibitory compounds are toxic to fermenting micro-organisms. The ethanol yield and productivity obtained during fermentation of lignocellulosic hydrolysates is decreased due to the presence of inhibiting compounds, such as weak acids, furans and phenolic compounds formed or released during thermo-chemical pre-treatment step such as acid and steam explosion. This review describes the application and/or effect of biological detoxification (removal of inhibitors before fermentation) or use of bioreduction capability of fermenting yeasts on the fermentability of the hydrolysates. Inhibition of yeast fermentation by the inhibitor compounds in the lignocellulosic hydrolysates can be reduced by treatment with enzymes such as the lignolytic enzymes, for example, laccase and micro-organisms such as Trichoderma reesei, Coniochaeta ligniaria NRRL30616, Trametes versicolor, Pseudomonas putida Fu1, Candida guilliermondii, and Ureibacillus thermosphaericus. Microbial and enzymatic detoxifications of lignocellulosic hydrolysate are mild and more specific in their action. The efficiency of enzymatic process is quite comparable to other physical and chemical methods. Adaptation of the fermentation yeasts to the lignocellulosic hydrolysate prior to fermentation is suggested as an alternative approach to detoxification. Increases in fermentation rate and ethanol yield by adapted micro-organisms to acid pre-treated lignocellulosic hydrolysates have been reported in some studies. Another approach to alleviate the inhibition problem is to use genetic engineering to introduce increased tolerance by Saccharomyces cerevisiae, for example, by overexpressing genes encoding enzymes for resistance against specific inhibitors and altering co-factor balance. Cloning of the laccase gene followed by heterologous expression in yeasts was shown to provide higher enzyme yields and permit production of laccases with desired properties for detoxification of lignocellulose hydrolysates. A combination of more inhibitor-tolerant yeast strains with efficient feed strategies such as fed-batch will likely improve lignocellulose-to-ethanol process robustness.     

SOME EFFECTS OF MONOAMINE OXIDASE INHIBITORS ON THE METABOLISM OF γ-AMINOBUTYRIC ACID IN RAT BRAIN

(1) The inhibitor of γ-aminobutyrate transaminase (GABA-T), amino-oxyacetic acid (AOAA), drastically reduced the activity of GABA-T to 30 per cent of the control value, with a corresponding increase of brain GABA, but had no effect on the activity of glutamate decarboxylase (GAD). (2) The monoamine oxidase (MAO) inhibitors phenelzine, phenylpropylhydrazine and phenylvalerylhydrazine, lowered GABA-T activity to 58, 49 and 48 per cent, respectively; this was associated with a marked elevation of brain GABA. (3) The action of phenelzine and phenylpropylhydrazine in vivo and in vitro could be abolished by pre-treatment of the tissue with the structurally related MAO inhibitors phenylisopropylhydrazine and trans-2-phenylcyclopropylamine. These had no action on the GABA system in vivo, either on the GABA content or on the GABA-T activity. These latter drugs, however, were unable to influence the effects of AOAA either on GABA or on GABA-T. (4) The possible mechanism of action on GABA and the enzyme activities of the GABA system is discussed.     

Inactivation of Buckwheat α-Glucosidase with 1-Ethyl-3-(3-dimethylaminopropyl) carbodiimide

The amino acid residue(s) involved in the activity of buckwheat α-glucosidase was modified by 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide in the presence of glycine ethyl ester. The modification resulted in the decrease in the hydrolytic activity of the enzyme following pseudo-first order kinetics. Competitive inhibitors, such as Tris and turanose, protected the enzyme against the inactivation. Protection was provided also by alkali metal, alkaline-earth metal and ammonium ions, though these cations are non-essential for the activity of the enzyme. Turanose or K⁺ protected one carboxyl group per enzyme from the modification with carbodiimide and glycine ethyl ester. Free sulfhydryl group of the enzyme was also partially modified with carbodiimide, but the inactivation was considered to be mainly attributed to the modification of essential carboxyl group rather than to that of free sulfhydryl group.     

Sulphonamide inhibition studies of the β-carbonic anhydrase from the bacterial pathogen Clostridium perfringens

The β-carbonic anhydrases (CAs, EC 4.2.1.1) from the pathogenic bacterium Clostridium perfringens (CpeCA) was recently characterised kinetically and for its anion inhibition profile. In the search of effective CpeCA inhibitors, possibly useful to inhibit the growth/pathogenicity of this bacterium, we report here an inhibition study of this enzyme with a panel of aromatic, heterocyclic and sugar sulphonamides/sulphamates. Some sulphonamides, such as acetazolamide, ethoxzolamide, dichlorophenamide, dorzolamide, sulthiame and 4-(2-hydroxymethyl-4-nitrophenyl-sulphonamido)ethylbenzenesulphonamide were effective CpeCA inhibitors, with K_Is in the range of 37.4–71.6?nM. Zonisamide and saccharin were the least effective such inhibitors, whereas many other aromatic and heterocyclic sulphonamides were moderate – weak inhibitors with K_Is ranging between 113 and 8755?nM. Thus, this study provides the basis for developing better clostridial enzyme inhibitors with potential as antiinfectives with a new mechanism of action.     

α-DIFLUOROMETHYL DOPA, A NEW ENZYME-ACTIVATED IRREVERSIBLE INHIBITOR OF AROMATIC L-AMINO ACID DECARBOXYLASE

DL-x-Difluoromethyl DOPA (DFMD, RMI 71801), an enzyme-activated irreversible inhibitor of aromatic L-amino acid decarboxylase in vitro, produces a rapid, long-lasting and dose-dependent inhibition of aromatic L-amino acid decarboxylase in peripheral tissues of mice when administered i.p. or orally. Doses of 500 mg/kg i.p. produce only very slight inhibition of the enzyme activity in mouse brain whilst inhibiting the enzyme activity of peripheral tissues by more than 90%. With L-[³H]-DOPA co-administration brain concentrations of L-[³H]DOPA and ³H-catecholamines are increased 3- to 8-fold concomitant with a decrease in the peripheral decarboxylation of L-[³H]DOPA. Under these conditions it is clear that the slight inhibition of enzyme activity in the brain is totally inadequate to inhibit the decarboxylation of L-DOPA in this organ. Similarly, the decarboxylation of exogenously supplied 5-hydroxytryptophan is inhibited peripherally with a consequent increase in brain serotonin concentrations. DFMD is another example of an enzyme-activated irreversible inhibitor which due to its novel and specific mechanism of action, may offer advantages over existing decarboxylase inhibitors.     

The neurosteroid allopregnanolone impairs object memory and contextual fear memory in male C57BL/6J mice

Allopregnanolone (ALLO, or 3α-hydroxy-5α-pregnan-20-one) is a steroid metabolite of progesterone and a potent endogenous positive allosteric modulator of GABA-A receptors. Systemic ALLO has been reported to impair spatial, but not nonspatial learning in the Morris water maze (MWM) and contextual memory in rodents. These cognitive effects suggest an influence of ALLO on hippocampal-dependent memory, although the specific nature of the neurosteroid's effects on learning, memory or performance is unclear. The present studies aimed to determine: (i) the memory process(es) affected by systemic ALLO using a nonspatial object memory task; and (ii) whether ALLO affects object memory via an influence within the dorsal hippocampus. Male C57BL/6J mice received systemic ALLO either before or immediately after the sample session of a novel object recognition (NOR) task. Results demonstrated that systemic ALLO impaired the encoding and consolidation of object memory. A subsequent study revealed that bilateral microinfusion of ALLO into the CA1 region of dorsal hippocampus immediately following the NOR sample session also impaired object memory consolidation. In light of debate over the hippocampal-dependence of object recognition memory, we also tested systemic ALLO-treated mice on a contextual and cued fear-conditioning task. Systemic ALLO impaired the encoding of contextual memory when administered prior to the context pre-exposure session. Together, these results indicate that ALLO exhibits primary effects on memory encoding and consolidation, and extend previous findings by demonstrating a sensitivity of nonspatial memory to ALLO, likely by disrupting dorsal hippocampal function.     

Purification and Properties of an S-PI(Pepstatin Ac)-insensitive Carboxyl Proteinase from a Xanthomonas sp. Bacterium

A S-PI(Pepstatin Ac)-insensitive carboxyl proteinase was found in culture filtrate of a Xanthomonas sp. bacterium. The carboxyl proteinase was highly purified and about 100 mg of the enzyme was obtained from 601 of culture filtrate, with a recovery of 25%. The optimum condition for the action of the purified enzyme toward casein was approx. pH 2.7 and its activity was not inhibited by any of such carboxyl proteinase inhibitors as Pepstatin, S-PI, and DAN but EPNP inhibited it. Such behavior of the enzyme against inhibitors resembles that of Pseudomonas sp. carboxyl proteinase, the first found from a bacterium. Some differences were observed, however, in their properties such as optimum pH, isoelectric point, and amino acid composition.     

The Effect of Metabolic Inhibitors, Sugars and Fusicoccin on the Electrical Potential Difference Arising Across an Intact Chenopodium Rubrum L. Plant

An analysis of the effect of metabolic inhibitors, sugars, and fusicoccin on the trans-plant electrical potential difference arising across one-week-old green or herbicide-treated Chenopodium rubrum L. plants was performed. The substances were applied either to the solution bathing the root or in the form of drops to the stem. The respiratory inhibitors (KCN and salicylhydroxamic acid), sulfhydryl agents (N-ethylmaleimide and p-chloromercuribenzene sulfonic acid) and proton ionophore (carbonyl cyanide m-chlorophenylhydrazone) affected the electrical potential, the kinetics of the induced changes varying with different inhibitors and site of application. None of the applied sugars (sucrose, glucose or sorbitol), ATPase stimulator fusicoccin or inhibitor vanadate exerted any appreciable effect on the electrical potential. An effect of sucrose could be observed in the case of its application immediately following de-rooting, especially in the case of herbicide-treated plants. These results we explain by non-participation of the sucrose transporter or the proton ATPase in the generation of the electrical potential difference across intact plants (apoplast-apoplast configuration).     

Cloning, expression, and enzymatic activity of Acinetobacter baumannii and Klebsiella pneumoniae acetyl-coenzyme A carboxylases

Pathogenic Gram-negative bacteria are a major public health concern because they are causative agents of life-threatening hospital-acquired infections. Due to the increasing rates of resistance to available antibiotics, there is an urgent need to develop new drugs. Acetyl-coenzyme A carboxylase (ACCase) is a promising target for the development of novel antibiotics. We describe here the expression, purification, and enzymatic activity of recombinant ACCases from two clinically relevant Gram-negative pathogens, Acinetobacter baumannii and Klebsiella pneumoniae. Recombinant ACCase subunits (AccAD, AccB, and AccC) were expressed and purified, and the holoenzymes were reconstituted. ACCase enzyme activity was monitored by direct detection of malonyl-coenzyme A (malonyl-CoA) formation by liquid chromatography tandem mass spectrometry (LC–MS/MS). Steady-state kinetics experiments showed similar k_cat and K_M values for both enzymes. In addition, similar IC₅₀ values were observed for inhibition of both enzymes by a previously reported ACCase inhibitor. To provide a higher throughput assay suitable for inhibitor screening, we developed and validated a luminescence-based ACCase assay that monitors ATP depletion. Finally, we established an enzyme activity assay for the isolated AccAD (carboxyltransferase) subunit, which is useful for determining whether novel ACCase inhibitors inhibit the biotin carboxylase or carboxyltransferase site of ACCase. The methods described here could be applied toward the identification and characterization of novel inhibitors.     

Cloning and overexpression of a thermostable signal peptide peptidase (SppA) from Thermoplasma volcanium GSS1 in E. coli

In this study, a gene coding for thermophilic serine protease of the ClpP class from the thermoacidophilic archaeon Thermoplasma volcanium (Tpv) was cloned and expressed in Escherichia coli. The primary sequence and domain analysis of this enzyme showed similarities (50–60% similarity) to signal peptide peptidases (SppA) of bacteria and other archaea. An increase of about tenfold in the activity was achieved by overexpression of Tpv SppA in E. coli, as detected by enzyme assays conducted using Ala-Ala-Phe-pNa and N-Suc-Ala-Ala-Pro-Phe-pNA as substrates. The recombinant enzyme, purified using an anion exchange column chromatography, displayed an apparent molecular mass of 26 kDa on SDS-PAGE analysis. Purified Tpv SppA was active in a broad range of pH and temperature with maximal activity at 60°C and between pH 7.5 and pH 8.0. The activity of the enzyme was strongly inhibited by inhibitors typical for serine proteases, i.e., chymostatin and PMSF. The activity of the Tpv SppA and the stability at high temperature were significantly enhanced in the presence of 5 mM Ca²⁺ ions. Our multiple sequence alignment data revealed a conserved Ser/Lys catalytic dyad in Tpv SppA that comprised Ser76 (nucleophile) and Lys128 (general base) residues. A search for a transmembrane domain using automated programs did not predict any signal peptide associated with the Tpv SppA and, therefore, suggested a cytoplasmic location for this enzyme.     

Inibitori nel Sarcotesta del Seme di Ginkgo Biloba E loro Azione Rallentatrice Sullo Sviluppo dell'embrione

Abstract

Inhibitors in the sarcotesta of GINKGO BILOBA seeds and their retarding action on embryo growth. — The sarcotesta of Ginkgo biloba seeds contains some inhibitors which delay or hamper the germination of other cormophytes seeds. This has been proved with seeds of Hordeum vulgare L., Vicia sativa L., and Triticum vulgare L. germinating in water extracts of ripe sarcotesta at various concentrations.

Water extracts of ripe sarcotesta at various concentrations have an anti-mitotic action on root apices of Allium cepa L., resulting in a marked preprophasic inhibition, chromosome stickiness, more or less evident c.-metaphases, and other effects. The water extracts were kept at their original pH (4–4,2) or alkalinized up to a pH of 6,4–6,6.

Indirect statistical evidence, which appears to be highly significant if tested with Student's t, shows that: i) in the seeds of Ginkgo themselves these inhibitors delay embryo development; ii) in the individual seeds of a same plant the inhibitory capacity of the sarcotesta affects embryo development at an earlier or later stage depending on how soon the sarcotesta ripens; iii) the action of the sarcotesta on the embryo decreases with a decreasing water content of the former.

The seeds of Ginkgo biloba do not go through a dormant phase but germinate as soon as the embryo is fully developed. It was already known that temperatures not sufficiently high have a retarding action on embryo growth in this species. This fact together with the presence of inhibitors in the sarcotesta can be interpreted as a biological defense against the danger of the seeds germinating in autumn and the seedlings or young plants dying during severe winter condition.     

An enzyme from the earthworm Eisenia fetida is not only a protease but also a deoxyribonuclease

The earthworm enzyme Eisenia fetida Protease-III-1 (EfP-III-1) is known as a trypsin-like protease which is localized in the alimentary canal of the earthworm. Here, we show that EfP-III-1 also acts as a novel deoxyribonuclease. Unlike most DNases, this earthworm enzyme recognizes 5′-phosphate dsDNA (5′P DNA) and degrades it without sequence specificity, but does not recognize 5′OH DNA. As is the case for most DNases, Mg²⁺ was observed to markedly enhance the DNase activity of EfP-III-1. Whether the earthworm enzyme functioned as a DNase or as a protease depended on the pH values of the enzyme solution. The protein acted as a protease under alkaline conditions whereas it exhibited DNase activity under acid conditions. At pH 7.0, the enzyme could work as either a DNase or a protease. Given the complex living environment of the earthworm, this dual function of EfP-III-1 may play an important role in the alimentary digestion of the earthworm.     

Possible Involvement of Cysteine and Histidine Residues in the (NH4 + + Na+)-Activated ATPase of an Anaerobic Alkaliphile, Amphibacillus xylanus

Effect of various inhibitors on the (NH₄ ⁺ + Na⁺)-activated ATPase of an anaerobic alkaliphile, Ep01(a strain of Amphibacillus xylanus), was examined. Among the chemicals tested, the enzyme was drastically inactivated by p-chloromercuribenzoic acid and diethyl pyrocarbonate. The ATPase activity of the enzyme, which was inactivated by p-chloromercuribenzoic acid and diethyl pyrocarbonate, was remarkably restored by β-mercaptoethanol and hydroxylamine, respectively, suggesting the involvement of cysteine and histidine residues in the enzyme activity. Analysis of the inhibition kinetics by diethyl pyrocarbonate indicated that modification of a single histidine residue per ATPase molecule was sufficient to inactivate the enzyme. Received: 2 June 1997 / Accepted: 7 July 1997     

Biochemical characterization of the γ-carbonic anhydrase from the oral pathogen Porphyromonas gingivalis,PgiCA

Abstract

Carbonic anhydrases (CAs, EC 4.2.1.1) catalyze a simple but physiologically relevant reaction in all life kingdoms, carbon dioxide hydration to bicarbonate and protons. CAs are present in many pathogenic species and are involved in the bicarbonate metabolism/biosynthetic reactions involving this ion. Ubiquity of these enzymes suggests a pivotal role in microbial virulence and pathogenicity. Porphyromonas gingivalis is an anaerobic bacterium, which colonizes the oral cavity, being involved in the pathogenesis of periodontitis, an inflammatory disease leading to tooth loss. Recently, we reported an anion inhibitory study on the γ-CA (denominated PgiCA) identified in the genome of this Gram-negative bacterium. In this paper we continue our research on PgiCA, and describe the biochemical characterization of the recombinant protein, its thermal stability, the oligomeric state and the enzyme kinetics. PgiCA is a polypeptide chain formed of 192 amino acids and displays an identity of 30–33% when compared with the prototypical γ-CAs, CAM or CAMH (from Methanosarcina thermophila) or CcmM (from Thermosynechococcus elongatus). A subunit molecular mass of 21?kDa was estimated by SDS-PAGE, while HPLC size exclusion chromatography under native conditions gave an estimated molecular mass of 65?kDa suggesting that the recombinant enzyme self-associate in a homotrimer, as all other γ-CAs studied so far. Enzyme kinetic analysis showed that PgiCA is 62 times more effective as a catalyst compared to CAM, the only other γ-CA characterized in detail kinetically. All these features represent an interesting attractive for the drug design of inhibitors/activators of this new enzyme.     

Comparative substrate-inhibitor analysis of mink liver monoamine oxidases

Comparative substrate-inhibitor analysis of catalytic properties of liver monoamine oxidases (MAO) was performed in the mature males of the American mink Mustela vison and the European mink Mustela lutreola. The action on the MAO activity was studied of alkaloids of the benzo[c]phenanthridine group: sanguinarine and chelidonine, diisoquinoline alkaloid berberine, medicinal agents “Ukrain” and “Sanguirythrin” as well as derivatives of 2-propylamine: deprenyl and chlorgylin. The latter turned out to be irreversible inhibitor of the MAO A form, whereas deprenyl-irreversible inhibitor of the MAO B form in both studied mink species. The selectivity of action of each inhibitor on the corresponding liver MAO form for the species M. vison was one order of magnitude stronger than for the species M. lutreola. All studied alkaloids as well medicinal agents on their basis have been shown to be specific irreversible inhibitors of the intermediate strength of the liver MAO A form of both mink species. They inhibit the enzymatic deamination of serotonin, tyramine, and tryptamine without affecting the deamination reaction of benzylamine and β-phenylethylamine (at concentrations of 10 mM and lower). Out of five studied isoquinoline agents, the medication “Ukrain” and alkaloid chelidonine have the highest inhibitory action; the agent “Sanguirythrin” and alkaloids berberine and sanguinarine produce the weaker monoamine oxidase effect. The revealed specificity of action of the studied inhibitors is an indirect evidence for the presence in the liver enzymes of both mink species, like in the rat liver enzyme, of several molecular forms.