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At least 109 records · Page 6Linked to original sources
PubMed1988

Correlates of diabetes markers with erythrocytic enzymes decomposing reactive oxygen species.

Superoxide dismutase (SOD), glutathione peroxidase (GPX) and catalase were assayed in the erythrocytes of a diabetic population on various treatment regimens (diet, oral therapy, and insulin), to investigate any relationships between their activities and diabetes markers (serum glucose, lipids, and fructosamine, as well as glycated haemoglobin). In the group of patients as a whole, there was significant negative correlation of SOD, but not of the other two enzymes with glycated haemoglobin and fructosamine. Specifically, there was a lower activity of the enzyme in the poorly-controlled patients. It is concluded that SOD in particular is potentially an additional marker for long-term diabetic pathophysiology.

Adult↗
PubMed1979

A technique for quantitating enzyme histochemistry in adjuvant arthritic joints. I. Alkaline phosphatase.

This paper establishes a quantitative technique for measuring the percentage of enzyme-reactive cells found in adjuvant arthritic articular cartilage, synovial membrane and bone marrow. Using alkaline phosphatase histochemistry and a recently-developed method of handling hard tissues, the technique is validated, the inherent variabilities determined and the existence of intra-articular lesions established. The technique now allows for a precise in situ evaluation of adjuvant arthritic drug inhibition by measuring enzyme-reactive cell alterations within the joint tissue most affected by the arthritis.

Alkaline Phosphatase↗
PubMed2005

Monitoring exposure of northern cardinals, Cardinalis cardinalis, to cholinesterase-inhibiting pesticides: enzyme activity, reactivations, and indicators of environmental stress.

Northern cardinals (Cardinalis cardinalis) frequently use agricultural field edges in northeast Arkansas, USA, and may be at risk of exposure to cholinesterase (ChE)-inhibiting pesticides. We monitored northern cardinal exposure to ChE-inhibiting pesticides by comparing plasma total ChE (TChE) activity to reference-derived benchmarks and TChE reactivations. Total ChE and acetylcholinesterase (AChE) were measured for 128 plasma samples from 104 northern cardinals from nine study sites. Of birds sampled from sites treated with ChE-inhibiting pesticides, 4.3% of the samples had TChE activities below the diagnostic threshold (2 standard deviations [SD] below the reference mean) and 8.7% of the samples had TChE reactivations. No difference was found in TChE (p = 0.553) and AChE (p = 0.288) activity between treated and reference sites; however, activity varied among treated sites (p = 0.003). These data do not suggest uniform exposure to individuals, but rather exposure was variable and likely influenced by mitigating factors at individual and site scales. Furthermore, monitoring of TChE reactivation appeared to be a more sensitive indicator of exposure than the diagnostic threshold. Fluctuating asymmetry (FA) was greater at agricultural sites than reference sites (p = 0.016), supporting the hypothesis that FA may be useful for assessing a combination of habitat- and contaminant-related environmental stress.

Acetylcholinesterase↗
PubMed1986

Comparative effects of wheat bran and barley husk on nutrient utilization in rats. 2. Zinc, calcium and phosphorus.

1. The present work was undertaken to study comparatively the effect on mineral availability in rats of wheat bran and barley husk when supplying the same amount of dietary fibre (DF). The experiment involved a total of nine dietary treatments including a control group and two series of four groups with increasing amounts of fibre from the two sources (total DF ranging from 42 to 117 g/kg dry matter (DM]. Dietary nitrogen concentration was kept constant at 15 g N/kg DM. Zinc concentration of the diets was adjusted to the level provided by the diet with the highest wheat-bran content (21 mg/kg DM) using zinc sulphate. Other minerals were not adjusted. 2. Two experiments were performed. In Expt 1 the diets were given to 5-week-old rats during 9 d and apparent absorptions of Zn, calcium and phosphorus and the femur concentrations of Zn, Ca and P were measured. In Expt 2 the diets were given to 9-week-old rats during 12 d. Mineral concentration in femur and total and albumin-bound plasma Zn and availability of plasma Zn for enzyme reactivation were measured. 3. In the younger animals, wheat bran depressed significantly the absorption of Zn when providing 40 g DF/kg DM and absorbtion of Ca when providing 80 g DF/kg DM. Barley husk depressed significantly both the absorption of Zn and Ca already at 20 g DF/kg DM. Both fibre sources had a more negative effect on Zn than on Ca absorption. Only barley husk had a small negative effect on absorption of P. Phytate did not appear as a major factor affecting mineral absorption in barley husk. All diets containing barley husk had a very low molar ratio, phytate:Zn. 4. The age of the animals influenced the utilization of dietary minerals using femur concentration as a criterion, particularly in the case of Zn. In the younger animals the decrease in femur Zn with fibre correlated with apparent Zn absorption both with wheat bran (R2 0.986, P less than 0.01) and with barley husk (R2 0.996, P less than 0.01). In the older animals femur Zn did not change significantly with fibre. 5. In the older animals, plasma Zn, albumin-bound plasma Zn and availability of plasma Zn for enzyme reactivation were lowest with the highest addition of wheat bran.

Absorption↗
PubMed1999

Role of edrophonium in prevention of the re-inhibition of acetylcholinesterase by phosphorylated oxime.

We examined the role of edrophonium in the acceleration phenomenon using mouse wild-type and mutant D74N AChE inhibited with 7-(O,O-diethyl-phosphinyloxy)-1-methylquinolinium methylsulfate (DEPQ). With DEPQ-inhibited wild-type mouse acetylcholinesterase (AChE), the reactivation kinetic profile demonstrated one-phase exponential association only when 2-[hydroxyimino methyl]-1-methylpyridinium chloride (2-PAM) and 1-(2-hydroxy-iminomethyl-1-pyridinium)-1-(4-carboxy-aminopyridi nium)-dimethyl ether hydrochloride (HI-6) were used as reactivators. When 1,1[oxybis-methylene)bis[4-(hydroxyimino)methyl] pyridinium dichloride (LüH6) and 1,1-trimethylene bis(4-hydroxyimino methyl) pyridinium dichloride (TMB4) were used, the reactivation kinetic profile was biphasic in nature. Edrophonium had no effect on reactivation by 2-PAM and HI-6, but significantly accelerated LüH6- and TMB4-induced reactivation of DEPQ-inhibited wild-type mouse AChE. Comparison of the initial and overall reactivation rate constants with five oximes indicated that acceleration by edrophonium may be due to the prevention of re-inhibition of the reactivated enzyme by the phosphorylated oxime (POX) produced during the reactivation. With LüH6 and TMB4, about 2.5-fold increase in the reactivation rate constants was observed in the presence of edrophonium, but little or no effect was observed with the other three oximes. The initial reactivation rate constants were 5.4- and 4.2-fold of the overall rate constants with LüH6 and TMB4 as reactivators respectively, however, very little change was found between the initial and overall rate constants with the other three oximes. In experiments with D74N AChE, for which the inhibition potency of charged organophosphate (OP) was two to three orders less than wild-type enzyme, edrophonium had no effect on the reactivation by LüH6 and TMB4 and the time courses of reactivation were monophasic. The data from mutant enzyme substantiate the involvement of edrophonium in protecting POX re-inhibition of reactivated enzyme formed during the reactivation of OP-inhibited AChE.

Animals↗
PubMed1978

Properties of taurine: alpha-ketoglutarate aminotransferase of Achromobacter superficialis. Inactivation and reactivation of enzyme.

The activity of taurine: alpha-ketoglutarate aminotransferase (taurine: 2-oxoglutarate aminotransferase, EC 2.6.1.55) from Achromobacter superficialis is significantly diminished by treatment of the enzyme with (NH4)2SO4 in the course of purification, and recovered by incubation with pyridoxal phosphate at high temperatures such as 60 degrees C. The inactive form of enzyme absorbing at 280 and 345 nm contains 3 mol of pyridoxal phosphate per mol. The activated enzyme contains additional 1 mol of pyridoxal phosphate with a maximum at 430 nm. This peak is shifted to about 400 nm as a shoulder by dialysis of the enzyme, but the activity is not influenced. The inactive form is regarded as a partially resolved form, i.e. a semiapoenzyme. The enzyme catalyzes transamination of various omega-amino aicds with alpha-ketoglutarate, which is the exclusive amino acceptor. Hypotaurine, DL-beta-aminoisobutyrate, beta-alanine and taurine are the preferred amino donors. The apparent Michaelis constants are as follows; taurine 12 mM, hypotaurine 16 mM, DL-beta-aminoisobutyrate 11 mM, beta-alanine 17 mM, alpha ketoglutarate 11 mM and pyridoxal phosphate 5 micron.

Alcaligenes↗
PubMed1993

Influence of nucleic acid base aromaticity on substrate reactivity with enzymes acting on single-stranded DNA.

Stacking between aromatic amino acids and nucleic acid bases may play an important role in the interaction of enzymes with nucleic acid substrates. In such circumstances, disruption of base aromaticity would be expected to decrease enzyme activity on the modified substrates. We have examined the requirement for DNA base aromaticity of five enzymes that act on single-stranded DNA, T4 polynucleotide kinase, nucleases P1 and S1, and snake venom and calf spleen phosphodiesterases, by comparing their kinetics of reaction with a series of dinucleoside monophosphates containing thymidine or a ring-saturated derivative. The modified substrates contained either cis-5R,6S-di-hydro-5,6-dihydroxythymidine (thymidine glycol) or a mixture of the 5R and 5S isomers of 5,6-dihydrothymidine. It was observed that for all the enzymes, except snake venom phosphodiesterase, the parent molecules were better substrates than the dihydrothymidine derivatives, while the thymidine glycol compounds were significantly poorer substrates. Snake venom phosphodiesterase acted on the unmodified and dihydrothymidine molecules at almost the same rate. These results imply that for all the remaining enzymes base aromaticity is a factor in enzyme-substrate interaction, but that additional factors must contribute to the poorer substrate capacity of the thymidine glycol compounds. The influence of the stereochemistry of the dihydrothymidine derivatives was also investigated. We observed that nuclease P1 and S1 hydrolysed the molecules containing 5R-dihydrothymidine approximately 50-times faster than those containing the S-isomer. The other enzymes displayed no measurable stereospecificity.

Acid Phosphatase↗
PubMed1976

Separation of subfragment-1 of H-meromyosin into two equimolar fractions with and without formation of the reactive enzyme-phosphate-ADP complex.

H-Meromyosin (HMM) was digested with insoluble papain [EC 3.4.22.2]. Neither the size of the initial burst of Pi liberation (0.5 mole/mole of myosin head) nor the Mg2+-ATPase [EC 3.6.1.3] activity of HMM in the steady state was affected by this treatment. Acto-S-1 was obtained by mixing F-actin with HMM digested with insoluble papain (HMM-S-1). The size of the initial burst of Pi liberation of acto-S-1 was 0.35 mole/mole of S-l at an ATP concentration of 0.5 mole/mole of S-1, and 0.5 mole/moleof S-1 at ATP concentrations above 1 mole/mole of S-1...

Actins↗
PubMed1976

Structure and function of the two heads of the myosin molecule. II. Separation of the two fractions of subfragment-1 of myosin by affinity column chromatography on immobilized F-actin: direct evidence for acceleration by F-actin of the decomposition of the reactive enzyme-phosphate-ADP complex formed on head B of myosin.

F-Actin (FA) and pyruvate kinase (PK) [EC 2.7.1.40] were immobilized on PAB-cellulose. HMM-Subfragment-1 (S-1) was applied to a column of immobilized FA and PK, and eluted with 1-1.5 muM ATP and 1 mM PEP in 50 mM KCl, 2 mM MgCl2, and 10 mM Tris-HCl at pH 7.8 and 4 degrees. The size of the initial burst of Pi liberation of S-1 applied to the column was 0.5 mole/mole S-1. The burst size of S-1 decreased with increase in the fraction number, and S-1 in later fractions showed a burst size of 0.1-0.3 mole/mole. On the other hand, the rate of the ATPase [EC 3.6.1.3] reaction in the steady state was almost independent of the burst size, and increased slightly with increase in the fraction number. The ATPase activity of S-1 with a burst size of less than 0.2 mole/mole was scarcely activated by FA. Usually, the dependence on the burst size of S-1 of its ATPase activity in the presence of FA was sigmoidal, and marked activation by FA was observed when the burst size was larger than 0.3-0.4 mole/mole. Similar results were obtained with S-1 fractions separated by the ultracentrifugation method described in our previous paper ((1976) J. Biochem. 79, 419-434).

Actins↗