Estuaries emit a large but highly uncertain amount of N2O into the atmosphere. To better understand cycling processes in estuaries, we provide first direct observations consumption seasonally anoxic Chesapeake Bay, largest estuary United States. rates waters reached up to 3.3 nmol L-1 d-1 were generally undetectable oxygenated waters. However, substantially enhanced when oxygen concentration wa...

Reliable estimates of Michaelis constants (K(m)) and inhibitor constants may be obtained, in the absence of control over the amount of enzyme being added to any assay system, provided the following constraints are met. Michaelis-Menten kinetics are obeyed. Two rate measurements must be made with the same sample of enzyme: at low and high substrate concentration for determining K(m) or minus and...

The concept of nitrogen (N) saturation has organized the assessment of N loading in terrestrial ecosystems. Here we extend the concept to lotic ecosystems by coupling Michaelis-Menten kinetics and nutrient spiraling. We propose a series of saturation response types, which may be used to characterize the proximity of streams to N saturation. We conducted a series of short-term N releases using a...

The kinetics of purified beef heart mitochondrial carnitine palmitoyltransferase have been extensively investigated with a semiautomated system and the computer program TANKIN and shown to be sigmoidal with both acyl-CoA and L-carnitine. In contrast, Michaelis-Menten kinetics were found with carnitine octanoyltransferase. The catalytic activity of carnitine palmitoyltransferase is strongly pH d...

The cytochrome P450s (CYPs) are the major enzymatic detoxification and drug metabolism system. Recently, it has become clear that several CYP isoforms exhibit positive and negative homotropic cooperativity. However, the toxicological implications of allosteric kinetics have not been considered, nor understood. The allosteric kinetics are particularly enigmatic in several respects. In many cases...

Lignocellulosic biomass is a potential source of renewable, low-carbon-footprint liquid fuels. Biomass recalcitrance and enzyme cost are key challenges associated with the large-scale production of cellulosic fuel. Kinetic modeling of enzymatic cellulose digestion has been complicated by the heterogeneous nature of the substrate and by the fact that a true steady state cannot be attained. We pr...

In metabolic networks, metabolites are usually present in great excess over the enzymes that catalyze their interconversion, and describing the rates of these reactions by using the Michaelis-Menten rate law is perfectly valid. This rate law assumes that the concentration of enzyme-substrate complex (C) is much less than the free substrate concentration (S0). However, in protein interaction net...

The or-chymotrypsin-catalyzed hydrolysis of p-nitrophenyl acetate has been studied at pH 7 and 25’ in isopropyl alcoholwater and dioxane-water mixtures. It was found that the initial reaction in which the enzyme is acylated follows second order kinetics rather than Michaelis-Menten kinetics as previously reported. The second order rate constant for this reaction is markedly decreased by additio...