Estimation of superoxide dismutase levels in saliva and gingival crevicular fluid among smokers and non-smokers in periodontitis patients - an observational study

Background: Smoking, which is an important risk factor for periodontitis, induces oxidative stress in the body and causes an imbalance between reactive oxygen species (ROS) and antioxidants, such as superoxide dismutase (SOD). The present study was done to quantify and compare the level of SOD enzyme levels in gingival crevicular fluid (GCF) and saliva among smokers and nonsmokers. Methodology: One hundred and thirty-five individuals in the age range of 20­55 years, including 45 light smokers, 45 heavy smokers, and 45 nonsmokers (controls), were selected and the clinical parameters recorded were plaque index, probing depth, and attachment loss. Smokers were divided into light smokers (<10 cigarettes/day) and heavy smokers (>10 cigarettes/day) and into three subgroups: healthy, mild periodontitis, and moderate periodontitis. GCF and saliva samples were collected then SOD levels were analyzed using spectrophotometric assay. Results: The mean levels of SOD in the GCF and saliva of smokers were decreased compared to controls. Intra- and inter-group analyses showed a significant reduction in the levels of SOD in the GCF and saliva of heavy smokers compared to light smokers and the control group. Conclusions: There was a progressive reduction in SOD levels from healthy nonsmokers to light smokers to heavy smokers

Purification, physicochemical and regulatory properties of serine hydroxymethyltransferase from sheep liver.

Serine hydroxymethyltransferase (EC 2.1.2.1) was purified from the cytosolic fraction of sheep liver by ammonium sulphate fractionation, CM-Sephadex chromatography, gel filtration using Ultrogel ACA 34 and Blue Sepharose affinity chromatography. The homogeneity of the enzyme was rigorously established by Polyacrylamide gel and sodium dodecyl sulphate-polyacrylamide gel electrophoresis, isoelectrofocusing, ultracentrifugation, immunodiffusion and Immunoelectrophoresis. The enzyme was a homotetramer with a molecular weight of 210,000 ±5000. The enzyme showed homotropic cooperative interactions with tetrahydrofolate (nH =2.8) and a hyperbolic saturation pattern with L-serine. At the lowest concentration of tetrahydrofolate used (0.2 mM), only 5% of the added folate was oxidized during preincubation and assay. The nH value was independent of the time of preincubation. Preincubation of the enzyme with serine resulted in a partial loss of the cooperative interactions (nH =1.6) with tetrahydrofolate. The enzyme was regulated allosterically by interaction with nicotinamide nucleotides; NADH was a positive effector while NAD+ was a negative allosteric effector. The subunit interactions were retained even at the temperature optimum of 60°C unlike in the case of the monkey liver enzyme, where these interactions were absent at higher temperatures. D-Cycloserine, a structural analogue of serine caused a sigmoid pattern of inhibition, in contrast with the observations on the monkey liver enzyme. Cibacron blue F3GA completely inhibited the enzyme and this inhibition could be reversed by tetrahydrofolate. Unlike in the monkey liver enzyme, NAD+ and NADH gave considerable protection against this inhibition. The sheep liver enzyme differs significantly in its kinetic and regulatory properties from the serine hydroxymethyltransferases isolated from other sources.