Glossary of Alpha-1 Terms

Enzymes / Proteins

Enzymes are a form of protein that can cause change or reaction in the body. Alpha-1 Antitrypsin (AAT) is an enzyme inhibitor and neutrophil elastase (NE) is an enzyme (both are proteins).  People often use the terms protein and enzyme interchangeably.

Genotype and Phenotype

People often use genotype and phenotype interchangeably but they are not exactly the same. The genotype identifies the genes that are inherited from each parent. The phenotype is the result of the genotype working in the body.

The easiest way to illustrate the difference is by an example. Suppose that you have had a blood test and been told that your phenotype is Z (or ZZ). You start taking augmentation therapy and sometime later another blood test is taken. Now your phenotype shows that you are MZ. How did you change from a ZZ to a MZ? It was due to the infusions that you were getting of the MM Alpha-1 protein. Now your genotype is ZZ and your phenotype is MZ. If you were to stop your infusions, your phenotype would revert to ZZ but your genotype would not change. It would still be ZZ.


Individuals with phenotypes that have two different genes; for example, MZ, MS, SZ, M-Null, etc, are heterozygotes.


Individuals who have two genes that are the same; for example, MM, ZZ, SS, Null-Null are classified as homozygotes.

Neutrophil Elastase

Neutrophil elastase (NE) is an enzyme that is found in the white blood cells. Its role is to destroy harmful foreign agents such as bacteria and viruses that could cause damage to the lungs and other organs. If it is not properly controlled, NE can attack and cause damage to healthy tissue, especially in the lungs.


(see Genotype above)

Protease Inhibitor

When patients receive their test results, the phenotype is often prefaced with the letters PI and then the letters for the genes (for example, PIZZ). The PI stands for Protease Inhibitor which is another, and more accurate, description for Alpha-1 Antitrypsin. However, Alpha-1 Antitrypsin was the name used first and it stuck.

Serum Level

The serum level identifies the amount of Alpha-1 Antitrypsin in the blood. Low levels indicate increased risk for developing disease.

DISCLAIMER:This website is designed to support, not replace, the relationship that exists between you and your physician. It is not the intention of this website to provide specific medical advice but rather to provide the Canadian Alpha-1 Community with information to better understand their health and their diagnosed disorder. Specific medical advice will not be provided and Alpha-1 Canada urges you to consult with a qualified physician for diagnosis and for answers to your personal questions.
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