Catalytic-activity content (cat.cont.) - Dynamic NPU Manual

Catalytic-activity content (cat.cont.)


Catalytic content



Definition in words

Catalytic-activity of component B divided by mass of system 1

Note: Component B is a catalytic component.

Definition by equation

Systematic terms

Catalytic-activity content of component B in system 1
Ratio scale
  • Value sets are positive numerical values
  • Algebraic operations are allowed (a=nb; a≠nb)
Numerical values from 0-∞


nkat/kg, µkat/kg, kat/kg, U/kg, kU/kg etc.

Note 1: Katal (abbreviated “kat”), is recommended unit for catalytic-activity kind-of-quantity. (katal=mol/s)

Note 2: Enzyme unit (abbreviated “U”) is acceptable for use (e.g. U, kU) but it is recommended to use katal. (Enzyme unit=µmol/min)

Special rule(s) in the NPU syntax

The catalytic component (component B) is termed according to the International Enzyme Nomenclature (see Medical and metrological vocabulary).

“Procedure” is stated in the specification to the kind-of-property in the NPU definition.

“Procedure” indicates that the measurement procedure must be stated somewhere else than the NPU code and there may be difficulties in comparing values for the same NPU code.


Ferard G, Dybkaer R, Fuentes-Arderiu X. Compendium of Terminology and Nomenclature of Properties in Clinical Laboratory Sciences : Recommendations 2016. 1 ed: Royal Society of Chemistry; 2016. 182 p. Doi:10.1039/9781782622451.

Laboratory field


Clinical Chemistry

Example 1
Generic abbreviated
NPU53521 Prot.(Tissue; Intestine)—Lactase; cat.cont.(37 °C; proc.) = ? kU/kg
Full result NPU53521 Protein(Tissue; Intestine)—Lactase; catalytic-activity content(37 °C; procedure) = 75 kiloEnzyme unit per kilogram
Abbreviated result NPU53521 Prot.(Tissue; Intestine)—Lactase; cat.cont.(37 °C; proc.) = 75 kU/kg
Written expression The catalytic-activity content of Lactase divided by mass of protein from Mr. Smith’s inestine tissue is  [75] kU/kg. The measurement is performed at 37 °C according to procedure defined by the laboratory.

Molecular Biology and Genetics

Example 2
Generic abbreviated
NPU17370 Lkc prot.—L-Iduronidase; cat.cont.(37 °C; proc.) = ? µkat/kg
Full result NPU17370 Leukocyte protein—L-Iduronidase; catalytic-activity content(37 °C; procedure) = 12 microkatal per kilogram
Abbreviated result NPU17370 Lkc prot.—L-Iduronidase; cat.cont.(37 °C; proc.) = 12 µkat/kg
Written expression The catalytic-activity content of L-Iduronidase of Mr. Smith leukocyte protein is [12] µkat/kg. The measurement is performed at 37 °C according to procedure defined by the laboratory.


NPU database, and
  • Kind-of-property

    • Nominal kind-of-property

    • Kind-of-quantity

      • Ordinal kind-of-quantity

      • Unitary kind-of-quantity

        • Rational unitary kind-of-quantity

          • Catalytic-activity content


  • Dybkaer R. Concept system on ‘quantity’: formation and terminology. Accredit Qual Assur. 2013;18(3):253-60.
  • Dybkaer R. ISO terminological analysis of the VIM3 concepts ‘quantity’ and ‘kind-of-quantity’. Metrologia. 2010;47(3):127-34.
Date Term Note
1996-01-01 Catalytical-activity content Term established
Date Notes


2019-06-04 Catalytic component B is an enzyme, defined by the international enzyme nomenclature (, and shall be used for catalytic-activity kinds-of-property. Proteins are defined and termed by UNIPROT ( and should not be used in relation to catalytic-activity kinds-of-property. Though there are overlaps between these two nomenclatures..

The enzyme and protein nomenclatures can have different terms for the same molecule.

  • ABC-type protein transporter (Enzyme nomenclature, identifier EC
  • Alpha-hemolysin (Protein nomenclature, UP identifier P09616).