decikatal
An SI unit of catalytic activity equal to 10⁻¹ katals. Symbol: d
decikatal: one-tenth of a katal, the SI unit for enzyme speed
A decikatal (dkat) is a unit of catalytic activity in the International System of Units, equal to 10 katals or 10 moles of substrate transformed per second. It measures how fast an enzyme or catalyst converts reactants into products. One decikatal represents a modest reaction rate; for perspective, a typical enzyme assay might produce activity readings in the range of microkatals to decikatals depending on the enzyme concentration and reaction conditions.
The katal itself was adopted into SI in 1999 to provide a standardized way of expressing enzyme activity across biochemistry, pharmaceuticals, and clinical diagnostics. Before that, enzymes were often reported in units like international units (IU) or specific activity expressed as moles per minute, leading to conversion headaches. The decikatal sits one order of magnitude below the base unit, making it useful for expressing moderate reaction rates without resorting to decimal notation.
Decikatal measurements appear most often in pharmaceutical quality control and clinical chemistry laboratories. An enzyme assay report might specify that a preparation contains 0.5 dkat/mL of lactate dehydrogenase, or that a bioreactor is running at 2.3 dkat/liter. Because enzyme activity is temperature and pH dependent, reported values should always reference the exact assay conditions used.
The prefix deci- means 10 to the power of negative one, following the standard SI metric hierarchy. Other common multiples of the katal include the microkatal (µkat), kilokata (kkat), and nanokatal (nkat). The symbol dkat is always written with a lowercase d and lowercase kat; deviations from this convention signal non-standard usage.
In practice, converting between decikatal and older enzyme units requires knowing the molecular weight of the substrate and the stoichiometry of the reaction. This conversion barrier is one reason some industries have been slow to adopt the katal despite its theoretical advantages. Regulatory bodies in the EU and others have mandated the use of katal and its multiples for enzyme activity declarations on pharmaceutical and diagnostic products.