Biomedical subjects

Nazmi Ozer

Publications and source records attributed to Nazmi Ozer.

6 recordsLinked to original sources

PubMed2004

Mitochondrial complex I and IV activities in leukocytes from patients with parkin mutations.

The parkin protein functions as a RING-type ubiquitin protein ligase. Considering the possibility that impaired ubiquitin-proteosomal system activity may impair antioxidant defenses and enhance oxidative stress, we have investigated the activity of mitochondrial respiratory enzymes in patients with parkin gene mutations. A significant decrease in the leukocyte complex I activity was found both in patients with parkin mutations (62.5%) and idiopathic PD (64.5%) compared with age-matched controls (P < 0.001). Complex IV activity was also decreased significantly in idiopathic PD patients (60%), but no difference was detected between controls and patients with parkin mutations.

Adult↗

PubMed2004

Partial purification and characterization of soluble isoform of butyrylcholinesterase from rat intestine.

Butyrylcholinesterase (BChE; E.C. 3.1.1.8.) was 260-fold purified from soluble fraction of rat intestine. The enzyme was composed of tetrameric globular form by nonreducing electrophoresis. Optimum pH value was determined as 7.2 after zero buffer extrapolation. Optimum temperature was examined as 37 degrees C after zero time extrapolation. The enzyme showed marked substrate activation with positively charged, acyl-choline substrates. As a measure of catalytic efficiency, kcat/Km values were determined as 16,210, 25,650, and 46,150 for acetylthiocholine (ATCh), propionylthiocholine (PTCh), and butyrylthiocholine (BTCh), respectively. When the catalytic efficiencies are compared, soluble isoform of rat intestinal BChE became increasingly efficient as the size of the acyl portion of the substrate increases; BTCh > PTCh > ATCh. Differently, the enzyme showed substrate inhibition with benzoylcholine (BzCh) and a kcat/Km value of 21,190 was found. Triton X-100 inhibited more efficiently the rat intestinal BChE soluble isoform than it did the human serum BChE.

Acetylthiocholine↗

PubMed2004

Purification and characterization of glucose-6-phosphate dehydrogenase from rat small intestine.

Glucose-6-phosphate dehydrogenase (G6PD) was purified from rat small intestine with 19.2% yield and had a specific activity of 53.8 units per miligram protein. The pH optimum was determined to be 8.1. The purified rat small intestinal G6PD gave one activity, one protein band on native PAGE. The observation of one band on SDS/PAGE with an Mr of 48 kDa and a specific activity lower than expected may suggest the proteolytically affected enzyme or different form of G6PD in the rat small intestine. The activation energy, activation enthalpy, Q10, and optimum temperature from Arrhenius plot for the rat small intestinal G6PD were found to be 8.52 kcal/mol, 7.90 kcal/mol, 1.59, and 38 degrees C, respectively. The Km values for G6P and NADP+ were 70.1 +/- 20.8 and 23.2 +/- 7.6 microM, respectively. Double-reciprocal plots of 1/Vm versus 1/G6P (at constant [NADP+]) and of 1/Vm versus 1/NADP+ at constant [G6P]) intersected at the same point on the 1/Vm axis to give Vm = 53.8 U/mg protein.

Animals↗

PubMed2003

Solid-phase enzyme modification via affinity chromatography.

In the present study antileukemic enzyme L-asparaginase (ASNase) and catalase (as a model enzyme) were modified in solid-phase with activated polyethylene glycol (PEG(2)) by using ligand-immobilized affinity column systems L-asparagine-Sepharose CL-4B and Procion red-Sepharose CL-4B, respectively. Studies on change of specific activity with modification time showed negligible differences between batches of modified catalase. Modification of ASNase for 1 h resulted in 50.2% recovery of the specific activity and the attachment of 69 molecules of PEG(2) per molecule of ASNase forming 'PEGylated ASNase'. Sequential modification of ASNase by activated PEG and heparin resulted in coupling of about nine molecules of heparin per molecule of PEGylated ASNase. Intravenous (i.v.) administration of PEG(2)-modified ASNase showed prolonged presence in the blood circulation and no adverse effects or symptoms of anaphylaxis were observed in presensitized mice.

Animals↗

PubMed2002

Dog liver glucose-6-phosphate dehydrogenase: purification and kinetic properties.

Glucose-6-phosphate dehydrogenase (G6PD) catalyses the first step of the pentose phosphate pathway which generates NADPH for anabolic pathways and protection systems in liver. G6PD was purified from dog liver with a specific activity of 130 U x mg(-1) and a yield of 18%. PAGE showed two bands on protein staining; only the slower moving band had G6PD activity. The observation of one band on SDS/PAGE with M(r) of 52.5 kDa suggested the faster moving band on native protein staining was the monomeric form of the enzyme. Dog liver G6PD had a pH optimum of 7.8. The activation energy, activation enthalpy, and Q10, for the enzymatic reaction were calculated to be 8.96, 8.34 kcal x mol(-1), and 1.62, respectively.The enzyme obeyed "Rapid Equilibrium Random Bi Bi" kinetic model with Km values of 122 +/- 18 microM for glucose-6-phosphate (G6P) and 10 +/- 1 microM for NADP. G6P and 2-deoxyglucose-6-phosphate were used with catalytic efficiencies (kcat/Km) of 1.86 x 10(6) and 5.55 x 10(6) M(-1) x s(-1), respectively. The intrinsic Km value for 2-deoxyglucose-6-phosphate was 24 +/- 4mM. Deamino-NADP (d-NADP) could replace NADP as coenzyme. With G6P as cosubstrate, Km d-ANADP was 23 +/- 3mM; Km for G6P remained the same as with NADP as coenzyme (122 +/- 18 microM). The catalytic efficiencies of NADP and d-ANADP (G6P as substrate) were 2.28 x 10(7) and 6.76 x 10(6) M(-1) x s(-1), respectively. Dog liver G6PD was inhibited competitively by NADPH (K(i)=12.0 +/- 7.0 microM). Low K(i) indicates tight enzyme:NADPH binding and the importance of NADPH in the regulation of the pentose phosphate pathway.

Animals↗

PubMedDate not supplied

Antioxidant enzymes in red blood cells and lymphocytes of ataxia-telangiectasia patients.

Toxic oxygen metabolites may contribute to the development of tissue damage, and play a role in the pathogenesis of malignancies, some acute and chronic pulmonary diseases, and in cell damage by radiomimetic agents, which can be seen in patients with ataxia-telangiectasia (A-T). Oxidative stress resulting from increased free radical production and/or defects in antioxidant defences is also involved in neurodegenerative disorders. Thus, oxidative stress could account for several aspects of the pleiotropic phenotype of A-T patients. The aim of this study was to determine the activities of the enzymes involved in cellular antioxidant metabolism in A-T patients to see if there is any defect which may result in constant oxidative stress. Superoxide dismutase (SOD) and catalase activities of erythrocytes, in contrast to lymphocytes, were found to be significantly higher in patients than in healthy controls. Our results may be another indication for the presence of constant oxidative stress in A-T patients as suggested previously.

Adolescent↗