Identification of glyoxalase 1 polymorphisms associated with enzyme activity

The glyoxalase system and its main enzyme, glyoxalase 1 (GLO1), protect cells from advanced glycation end products (AGEs), such as methylglyoxal (MG) and other reactive dicarbonyls, the formation of which is increased in diabetes patients as a result of excessive glycolysis. MG is partly responsible for harmful protein alterations in living cells, notably in neurons, leading to their dysfunction, and recent studies have shown a negative correlation between GLO1 expression and tissue damage. Neuronal dysfunction is a common diabetes complication due to elevated blood sugar levels, leading to high levels of AGEs. The aim of our study was to determine whether single nucleotide polymorphisms (SNPs) in the GLO1 gene influence activity of the enzyme. In total, 125 healthy controls, 101 type 1 diabetes, and 100 type 2 diabetes patients were genotyped for three common SNPs, rs2736654 (A111E), rs1130534 (G124G), and rs1049346 (5′-UTR), in GLO1. GLO1 activity was determined in whole blood lysates for all participants of the study.     

Human monoamine oxidase A gene determines levels of enzyme activity.

Monoamine oxidase (MAO) is a critical enzyme in the degradative deamination of biogenic amines throughout the body. Two biochemically distinct forms of the enzyme, A and B, are encoded in separate genes on the human X chromosome. In these studies we investigated the role of the structural gene for MAO-A in determining levels of activity in humans, as measured in cultured skin fibroblasts. The coding sequence of the mRNA for MAO-A was determined by first-strand cDNA synthesis, PCR amplification, and direct dideoxy sequencing. Two single-basepair substitutions were observed in cDNAs from cells with a 30-fold difference in activity levels. These two substitutions were in the third base of a triplet codon and hence did not affect the deduced amino acid sequence but did affect the presence or absence of restriction-enzyme sites for EcoRV and Fnu4HI, which could be elucidated on PCR fragments derived from genomic DNA or cDNAs. A third polymorphism for MspI in the noncoding region of the MAOA gene was also evaluated by Southern blot analysis using genomic DNA. Statistically significant associations were observed between the alleles for MAOA and levels of MAO activity in human male fibroblast lines. This association indicates that the MAOA gene itself is a major determinant of activity levels, apparently, in part, through noncoding, regulatory elements.     

Monoamine oxidase activity in hepatopancreas of Octopus vulgaris

1. Monoamine oxidase activity has been studied in hepatopancreas of Octopus vulgaris using 5-HT and PEA as substrates.2. Time courses of MAO activity against 5-HT and PEA show that the enzyme has higher affinity for PEA than for 5-HT.3. MAO activity against 5-HT appears more sensitive than MAO activity against PEA, to variations of the temperature (range 17–67°C).4. The inhibition curves obtained with clorgyline and deprenyl indicate that MAO activity is due to a single form of the enzyme, not corresponding to type A and type B MAO.5. Semicarbazide 10⁻⁴ M does not affect the deamination of 5-HT and PEA, demonstrating that a semicarbazide-sensitive amine oxidase is not involved in this process.     

Monoamine oxidase and catechol-O-methyl transferase activity in Tetrahymena.

Tetrahymena pyriformis strain HSM was found to have monomine oxidase (MAO) and a catechol-3-methyl transferase-like (COMT) activity. As in mammalian tissues, the MAO activity is predominantly localized in the mitochondrial pellet and COMT in the cytosol. The COMT-like activity was present in amounts comparable to several mouse tissues and was inhibited by tropolone. MAO activity was much lower than in any of the mouse tissues tested, and its activity varied greatly from preparation to preparation. The substrate preference of Tetrahymena MAO was tryptamine greater than serotonin greater than dopamine, and activity increased with increasing pH from pH 6.5 to pH 7.8, as does that of mouse liver MAO. Teh Km of Tetrahymena MAO for tryptamine was approximately 4 micrometer, an order of magnitude lower than that of mouse liver MAO. Sensitivity of inhibition by MAO inhibitors was variable. In some preparations, no inhibition was observed. In others clear inhibition was obtained, harmine and clorgyline being among the most potent inhibitors.     

Innate immunity functional gene polymorphisms and gout susceptibility

Gout is a common autoinflammatory disease characterized with elevated serum urate and recurrent attacks of intra-articular crystal deposition of monosodium urate. Accumulating evidence has demonstrated that MSU crystal-induced inflammation is a paradigm of innate immunity and the TLRs, NALP3 inflammasome and IL1R pathways are involved in gout development. Innate immunity components containing TLR2, TLR4, CD14, NALP3, ASC, Caspase-1 and CARD-8 are essential in the development of gouty inflammation. Recent studies suggest that innate immunity component gene functional mutations contribute to the development of autoinflammatory diseases including hereditary periodic fever syndrome, arthritis as well as inflammatory bowel disease. Taking into account these genetic findings, we would like to propose a novel hypothesis that the gene functional mutations might make innate immunity components as attractive susceptibility candidates and genetic markers for gout. Further clinical genetic studies need to be performed to confirm the role of innate immunity in the etiology of gout.     

Monoamine oxidase B activity is increased in human gliomas

Glial tumours are the most common type of brain neoplasm in humans. Tumour classification and grading represent key factors for patient management. However, current grading schemes are still limited by subjective histological criteria. In this context, gliosis has been linked to increases in monoamine oxidase B (MAO-B) activity. Thus, in the present study, MAO-B activity in membranes of glial tumours (n=20), meningiomas (n=12) and non-pathological human brains (n=15) was quantified by [14C]PEA oxidation. MAO-B activity was significantly greater in glioblastoma multiformes than in postmortem control brains (p<0.01) or meningiomas (p<0.001). There were no significant differences in MAO-B activity between glioblastoma multiformes (n=11) and low-grade astrocytomas (n=3) or anaplastic astrocytomas (n=6). In conclusion, the present results demonstrate a significant and selective increase in MAO-B activity in human gliomas when compared with meningiomas or non-tumoural tissue. These results suggest that the quantification of MAO-B activity may be a useful diagnostic tool for differentiating glial tumours from other types of brain tumours or surrounding normal brain tissue.     

Monoamine oxidase activity of rat brain under cold exposure

Cold stress and cold adaptation were studied for their effect on the activity and substrate specificity of the monoamine oxidase A and B and on the Km of serotonin deamination in the rat brain mitochondria and supernatant. Mitochondrial monoamine oxidase Km with serotonin is established to increase more than twice under cold stress and decrease considerably in cold adapted rats. The lowering of the mitochondrial monoamine oxidase A activity is accompanied by the appearance of serotonin and the glucosamine deaminating activity in supernatant. The data suggest that decrease in the monoamine oxidase activity under cold stress may be caused by both release of the enzyme from mitochondrial membrane and changes in its catalytic property alteration.