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Introduction: this paper examines the case of prescription enteral nutritional support tube in Colombia, analyzed from the perspective of the Social Security System in Health, and explained as the result of a problem of institutional coordination. The role and incentives of different actors are identified and shown how the interaction of these discourages the use of enteral nutrition in cases where it is necessary, with corresponding clinical effect for the patient and increased cost for the system., Methods: analysis of the effects it may have in clinical practice the problem of institutional coordination of regulators in the country, analyze their origin and the incentives and interests of the various stakeholders, prior synthesis of the relevant literature review. The search was conducted in the following databases: PubMed, Medline, and Embase ScienceDirect., Conclusions: the current situation of enteral nutritional support in Colombia is the result of a suboptimal equilibrium, resulting from a problem of institutional coordination that can only be solved when the agents to look beyond their local incentives, and nutritional support is a key component of hospital care and constitutes a means to the end: the health of the population served., (Copyright AULA MEDICA EDICIONES 2014. Published by AULA MEDICA. All rights reserved.)

The effect of NADH on melanogenesis under aerobic conditions involves three types of reaction: (a) acting as tyrosinase substrate (a competitive substrate of L-tyrosine and L-DOPA), (b) irreversible inactivation acting as a suicide substrate of tyrosinase, and (c) non-enzymatic reduction of o-dopaquinone by NADH. Under anaerobic conditions, NADH irreversibly inhibits the enzymatic forms met-tyrosinase and deoxy-tyrosinase. In this paper, we kinetically characterize this coenzyme as it acts as a tyrosinase suicide substrate and propose a kinetic mechanism to explain its oxidation by tyrosinase. In addition, the compound is characterized as an irreversible inhibitor of met-tyrosinase and deoxy-tyrosinase.

Carbidopa and benserazide have been described as inhibitors of dopa decarboxylase and both have been used in the treatment of Parkinson's disease. Because of their chemical structure as polyphenols, these compounds can behave as substrates of tyrosinase and peroxidase. We demonstrate that these enzymes oxidize both substrates. Since o-quinones are unstable, a chronometric method for enzymatic initial rate determinations was used based on measurements of the lag period in the presence of micromolar concentrations of ascorbic acid to kinetically characterize these substrates. In the case of tyrosinase, the values of the Michaelis constant for both substrates were greater than those described for dopa, although the catalytic constants were lower, probably due to the greater size of the substitute group in carbon 1. As regards peroxidase, the saturation of the enzyme by both substrates is possible, however this effect does not occur with the isomers of dopa. The distance of the charges from the benzene ring may enable the ring to approach the iron of the active site and, therefore, act.