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In chemistry, the term "turnover number" has two distinct meanings.. In enzymology, the turnover number (k cat) is defined as the limiting number of chemical conversions of substrate molecules per second that a single active site will execute for a given enzyme concentration [E T] for enzymes with two or more active sites. [1]
The katal (symbol: kat) is that catalytic activity that will raise the rate of conversion by one mole per second in a specified assay system. [1] It is a unit of the International System of Units (SI) [1] used for quantifying the catalytic activity of enzymes (that is, measuring the enzymatic activity level in enzyme catalysis) and other catalysts.
The rate of a reaction is the concentration of substrate disappearing (or product produced) per unit time (mol L −1 s −1). The % purity is 100% × (specific activity of enzyme sample / specific activity of pure enzyme). The impure sample has lower specific activity because some of the mass is not actually enzyme.
For a kinetically perfect enzyme, every encounter between enzyme and substrate leads to product and hence the reaction velocity is only limited by the rate the enzyme encounters substrate in solution. Hence the upper limit for / is equal to rate of substrate diffusion which is between 10 8 and 10 9 s −1 M −1. [2]
The enzyme unit, or international unit for enzyme (symbol U, sometimes also IU) is a unit of enzyme's catalytic activity. [1]1 U (μmol/min) is defined as the amount of the enzyme that catalyzes the conversion of one micro mole of substrate per minute under the specified conditions of the assay method.
1.15078 miles per hour (approximately), 20.25372 inches per second (approximately) 1.68781 feet per second (approximately). The length of the internationally agreed nautical mile is 1 852 m. The US adopted the international definition in 1954, having previously used the US nautical mile (1 853.248 m). [6]
≡ 1 m/s = 1 m/s mile per hour: mph ≡ 1 mi/h = 0.447 04 m/s: mile per minute: mpm ≡ 1 mi/min = 26.8224 m/s: mile per second: mps ≡ 1 mi/s = 1 609.344 m/s: speed of light in vacuum: c: ≡ 299 792 458 m/s = 299 792 458 m/s: speed of sound in air: s: 1225 to 1062 km/h (761–660 mph or 661–574 kn) [note 1] ≈ 340 to 295 m/s: Note
Conversion of units is the conversion of the unit of measurement in which a quantity is expressed, typically through a multiplicative conversion factor that changes the unit without changing the quantity. This is also often loosely taken to include replacement of a quantity with a corresponding quantity that describes the same physical property.