We investigated the potential role of the co-substrate, thiocyanate (SCN–), in modulating the catalytic activity of myeloperoxidase (MPO) and other members of the mammalian peroxidase superfamily (lactoperoxidase (LPO) and eosinophil peroxidase (EPO)). Pre-incubation of SCN– with MPO generates a more complex biological setting, because SCN– serves as either a substrate or inhibitor, causing diverse impacts on the MPO heme iron microenvironment. Consistent with this hypothesis, the relationship between the association rate constant of nitric oxide binding to MPO-Fe(III) as a function of SCN– concentration is bell-shaped, with a trough comparable with normal SCN– plasma levels. Rapid kinetic measurements indicate that MPO, EPO, and LPO Compound I formation occur at rates slower than complex decay, and its formation serves to simultaneously catalyze SCN– via 1e– and 2e– oxidation pathways. For the three enzymes, Compound II formation is a fundamental feature of catalysis and allows the enzymes to operate at a fraction of their possible maximum activities. MPO and EPO Compound II is relatively stable and decays gradually within minutes to ground state upon H2O2 exhaustion. In contrast, LPO Compound II is unstable and decays within seconds to ground state, suggesting that SCN– may serve as a substrate for Compound II. Compound II formation can be partially or completely prevented by increasing SCN– concentration, depending on the experimental conditions. Collectively, these results illustrate for the first time the potential mechanistic differences of these three enzymes. A modified kinetic model, which incorporates our current findings with the mammalian peroxidases classic cycle, is presented.

Within 16 year-period secular trend in seven measurements of physical growth of male children and youth from Tuzla Region, was researched by corresponding analysis of the sample that involved 1329 researched subjects. Our data were compared with the results of research from 1980 in the sample of 1349 boys. Nine successive generations in 1980 and 1996, from Tuzla region, were involved in this research. Analysis of the data obtained is based primarily on scientific elaboration of the situation registered in 1996 in the tested part of the broader population, after an unnatural and extremely unfavorable period for physical growth of the large majority of that population. The aim of this research was to establish secular trend (negative or positive) for the seven measurements of physical growth of male children and youth comparing our results from 1996 to corresponding research results on growth and development from1980, the sample of about same population (nearly same number of investigated persons). Although the unfavorable war living conditions negatively affected ontogenesis of the researched subjects, body dimensions of male children and youth were established as harmonious, in the limits of average European standards. However, it seems the unfavorable living conditions caused temporary slowdown in body dimensions, so, for these generations (11 to 19 years old), we could not find any increase of mean values (for certain number) of the researched parameters in comparison with the sample from 1980 year. So, 16 year-acceleration trend for most parameters was established and it is particularly evident inpost pubertal period.