enzyme activity

Enzymes are proteins that carry an electrical charge. Interestingly, they have a life span that begins and ends similar to the batteries we use in our everyday electronics. Enzymes circulate in the body by interacting with certain substrates until their charge is simply used up. Enzymes can also be exhausted in bodily reactions or degraded slowly even if they remain inactive. To determine the potency or (charge) of a particular enzyme certain tests called assays are performed.


There are two characteristics that change an enzymes potency; namely enzyme activity and dilution. Enzyme potency is also different depending on storage procedures as well as its quality and dilution strengths. Serrapeptase, however, is a special enzyme that comes in all strengths and concentrations. This section describes why using an IU or International Unit of measurement for vitamins cannot be used to accurately describe the quality of enzymes and their activity.


Understanding Serrapeptase Enzyme Activity – SPU, SU and IU


If you have been searching the web for information about Serrapeptase and other systemic enzyme supplements, you probably have run into the abbreviations SPU, SU and/or IU in relation to a Serrapeptase product's potency. Since an enzyme's potency is the number one factor in determining how well it works, understanding what these measurements mean and how they relate to each other is essential in order to be able to compare Serrapeptase enzyme supplements, choose the most effective one, and to take an effective dosage.


SPU (serratiopeptidase units) and SU (serrapeptase units) are essentially the same units and can be used interchangeably (although SPU is generally used more often than SU). Both SPU and SU measure the activity or potency of the Serrapeptase enzyme based on a specific scientific test. Therefore, SPU and SU are considered the 'active units' of Serrapeptase. "S" represents Serrapeptase and "SP" represents Serratiopeptidase in this case, virtually 2 acronyms for the exact same enzyme. Since several enzymes begin with the letter S, SP has been adopted as the more common abbreviation for Serrapeptase.


Many companies use IU, or international units, when describing the activity of their Serrapeptase enzyme supplements. However, IUs are a completely different measurement than SPU or SU. An IU is defined as the quantity of a biological substance (usually a vitamin or hormone) that produces a specific biological effect that has been agreed upon as an international standard. Despite its name, IU is not part of the International System of Units used in physics and chemistry. The IU should not be confused with the enzyme unit, also known as the International unit of enzyme activity and abbreviated as U.


Although IUs are a measure of potency, they can't be used to describe enzymes. This is because the method for measuring the potency of the Serrapeptase enzyme and other enzymes isn't the same as measuring the potency of a vitamin. For Serrapeptase, it isn't the quantity (usually measured in milligrams or mg) that counts; rather, it is the amount of fibrin or other proteins that Serrapeptase can break down or digest that determines its potency.


All of this may seem a little technical, but here's the bottom line to clear up any confusion you may have – the proper measurement for Serrapeptase enzyme activity is SPU or SU since it is based on a test specifically designed for this enzyme. Any product or website stating that measurements listed in SPU and SU are considerably less potent than those measured in IU are completely false and misleading. Look for Serrapeptase brands with higher SPUs or SUs to get a higher Serrapeptase dosage.

IU = Used for vitamins and minerals; was developed by the Expert Committee on Biological Standardization which is a functioning body of World Health Organization.


U = Used for enzymes; was developed by the International Union of Biochemistry and Molecular Biology (IUBMB).



  1. How does an IU compare to an SU?
    Technically there is no International Units for enzymes, so you really cannot compare the two units of measurement. Many companies assume that the SU denotes or equates to the international unit for Serrapeptase. So they blindly use the IU to denote SU. As confusing as this sounds, most companies are mistakenly using IU instead of SU to rate their Serrapeptase product, thinking that they are the same measurement.
  2. What is better an SU or an IU?
    It's really hard to say. It is possible some companies think the IU is the international unit for Serrapeptase and in this case they would be the same. Since this is not always the case, it is better to simply stay away from companies that do not know how to properly label their ingredients. In short, only buy Serrapeptase rated in SU or SPU, as these are the recognized activity assays used to rate the Serrapeptase enzyme.


Enzyme unit