Biochemical information about the ubiquitous pteridines has become generally available only within the last fifteen years. This delay can be traced to the chemical lability of these compounds and their small concentrations in organisms. New methods of isolation and isotopic techniques have provided data on the biosynthesis, anabolism, and catabolism of this class of compounds. Hydrogenated pteridines are recognized today as cofactors for various mixed function oxygenases and are involved in cellular electron transport. Further unknown catalytic functions for pteridines in cellular metabolism are indicated by their physiological activity, negative redox potentials, and histoautoradiographic data.
Two types of urine protein dipsticks and the sulfosalicylic acid method were compared for their accuracy and specificity, with use of urine samples supplemented with various proteins. Dipsticks yield accurate results when the protein under consideration is restricted to albumin; the sulfosalicylic acid method accurately determines many kinds of proteins in addition to albumin. Detergents affect each of the methods, but changes in salt concentration only affect results by dipstick procedures. Dipsticks, which are based on the protein-error principle for indicators, are subject to some of the conditions that apply to the bromcresol green method for serum albumin determination.
Chemische Labilitat und eine zumeist ungewohnlich niedrige biologische Konzentration sind die Hauptgriinde, warum die Biochemie der offenbar ubiquitaren Pteridine erst im Verlauf der letzten funfzehn Jahre experimentell zuganglich wurde. Neben schonenden Isolierungsmethoden brachte vor allem die Isotopentechnik Erkenntnisse uber Biosynthese, Anabolismus und Katabolismus dieser Stoflklasse. Hydrierte Pterine sind Cofaktoren mehrerer mischfunktioneller Oxygenasen und sind am zellularen Elektronentransport beteiligt. Das physiologische Verhalten, das negative Redoxpotential und histoautoradiographische Daten sprechen fur eine Rcihe weiterer, bisher noch unbekannter katalytischer Funktionen der Pteridine im Zellstoffwechsel.
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