What is the SI unit of enzyme activity?

What is the SI unit of enzyme activity?

• A. Katal (mol/s)
• B. IU (μmol/min)
• C. Unit (μmol/min)
• D. Katal (μmol/s)

Answer: (A)

Enzyme activity is a rate—how much substrate is converted per unit time. The SI unit for this rate is the katal, defined as 1 mole of substrate converted per second. This uses SI base quantities (moles and seconds) and is the formal standard for catalytic activity. Other units like the international unit (IU) or a generic Unit are non-SI and are typically defined as μmol of substrate per minute, which isn’t part of the SI system. Saying katal in terms of μmol per second isn’t standard, because 1 katal equals 1 mole per second, so expressing it as μmol/s would just represent a different magnitude (1 μmol/s is 1e-6 katal). Therefore, the SI unit is katal (mol/s).

Enzyme activity is a rate—how much substrate is converted per unit time. The SI unit for this rate is the katal, defined as 1 mole of substrate converted per second. This uses SI base quantities (moles and seconds) and is the formal standard for catalytic activity. Other units like the international unit (IU) or a generic Unit are non-SI and are typically defined as μmol of substrate per minute, which isn’t part of the SI system. Saying katal in terms of μmol per second isn’t standard, because 1 katal equals 1 mole per second, so expressing it as μmol/s would just represent a different magnitude (1 μmol/s is 1e-6 katal). Therefore, the SI unit is katal (mol/s).