What is the Difference Between Alkaline Phosphatase and Bone-Specific Alkaline Phosphatase

The key difference between alkaline phosphatase and bone-specific alkaline phosphatase is that alkaline phosphatase is an enzyme that is found in the liver,  bile duct, bones,  kidneys, intestine, and placenta of pregnant women, while bone-specific alkaline phosphatase is the bone-specific isoform of alkaline phosphatase that is found on the surface of osteoblasts of bone.

Alkaline phosphatase and bone-specific alkaline phosphatase are two related glycoprotein molecules. Both play very important enzymatic functions in the human body.

CONTENTS

1. Overview and Key Difference
2. What is Alkaline Phosphatase 
3. What is Bone-Specific Alkaline Phosphatase
4. Similarities – Alkaline Phosphatase and Bone-Specific Alkaline Phosphatase
5. Alkaline Phosphatase vs Bone-Specific Alkaline Phosphatase in Tabular Form
6. Summary – Alkaline Phosphatase vs Bone-Specific Alkaline Phosphatase

What is Alkaline Phosphatase?

Alkaline phosphatase (ALP) is an enzyme that is found throughout the human body. ALP is often considered a liver enzyme. This is because it is primarily found in the liver. But it can also be seen in the bile duct, bones, kidneys, intestine, and placenta. This enzyme plays a very important role in metabolism within the liver and is also involved in the development of the skeleton.

The normal ALP level in the blood is 44 to 147 international units per litre (IU/L) or 0.73 to 2.45 microkatal per litre (µkat/L). Abnormal levels of ALP in the blood reflect the damage to tissue or disruption of normal bodily processes. Moreover, high levels of ALP may indicate liver disease or bone disorders. There are two main tests that can be done to measure ALP levels: the ALP test and the ALP isoenzyme test. ALP test is a very common and essential part of medical testing and screening. The ALP test carries a low risk, with the main potential side effect being the occurrence of slight tenderness or a bruise at the blood draw site.

What is Bone-Specific Alkaline Phosphatase?

Bone-specific alkaline phosphatase is the bone-specific isoform of alkaline phosphatase. It is a glycoprotein (enzyme) found on the surface of osteoblasts in the bone. This enzyme indicates the biosynthetic activity of osteoblasts (bone-forming cells). This enzyme is highly expressed in the cells of mineralized tissue and plays a crucial role in the formation of hard tissue.

Bone-specific alkaline phosphatase can be measured by using a normal blood test called ALP isoenzyme test. The normal reference of bone-specific alkaline phosphatase for 25 years and older is 6.5-20.1 µg/L. Furthermore, high levels of bone-specific alkaline phosphatase indicate bone disorders such as osteoporosis and Paget disease.

What are the Similarities Between Alkaline Phosphatase and Bone-Specific Alkaline Phosphatase?

• Alkaline phosphatase and bone-specific alkaline phosphatase are two related glycoprotein molecules.
• Both play very important enzymatic functions in the human body.
• Normal blood tests can measure the levels of both.
• The high levels of both in the blood indicate different disorders.

What is the Difference Between Alkaline Phosphatase and Bone-Specific Alkaline Phosphatase?

Alkaline phosphatase is an enzyme found in the liver, bile duct, bones, kidneys, intestine, and placenta in pregnant people, while bone-specific alkaline phosphatase is the bone-specific isoform of alkaline phosphatase found on the surface of osteoblasts of bone. Thus, this is the key difference between alkaline phosphatase and bone-specific alkaline phosphatase. Moreover, alkaline phosphatase levels in the blood can be measured by the ALP test. On the other hand, bone-specific alkaline phosphatase levels in blood cancer are measured by the ALP isoenzyme test.

The infographic below presents the differences between alkaline phosphatase and bone-specific alkaline phosphatase in tabular form for side-by-side comparison.

Summary – Alkaline Phosphatase vs. Bone-Specific Alkaline Phosphatase

Alkaline phosphatase is an enzyme found in many parts of the human body. It is primarily found in the liver. But it is present in other parts, as well. Therefore, alkaline phosphatase and bone-specific alkaline phosphatase are two related glycoprotein molecules. Alkaline phosphatase is found throughout the human body, including the liver, bile duct, bones, kidneys, intestine, and placenta of pregnant women, while bone-specific alkaline phosphatase is the bone-specific isoform of alkaline phosphatase that is found on the surface of osteoblasts in the bone. Moreover, abnormal alkaline phosphatase level in the blood indicates liver disease or certain bone disorders, whereas abnormal bone-specific isoform of alkaline phosphatase indicates bone disorders such as osteoporosis and Paget disease. So, this summarizes the difference between alkaline phosphatase and bone-specific alkaline phosphatase.

Reference:

1. “Alkaline Phosphatase.”  Statpearls – NCBI Bookshelf.
2. “Bap – Overview: Bone Alkaline Phosphatase, Serum.” Mayo Clinic Labs.

Image Courtesy:

1. “PLAP 1ZEF dimer” By E A S – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Alkaline phosphatase – 2” By Madhero88 at English Wikipedia (CC BY-SA 3.0) via Commons Wikimedia