What is the Difference Between Acid Phosphatase and Alkaline Phosphatase

The key difference between acid phosphatase and alkaline phosphatase is that acid phosphatase is a phosphatase enzyme that is optimally active in an acidic pH, while alkaline phosphatase is a phosphatase enzyme that is optimally active in an alkaline pH.

Phosphatase is the enzyme that catalyzes the hydrolysis of phosphoric esters (phosphoric acid monoester). This reaction liberates an inorganic phosphate and an alcohol. Phosphatase is a subcategory of hydrolases.  It is highly essential for biological functions such as cellular regulation and signalling. Due to the prevalence of phosphatase in cellular regulation, it is an area of interest for pharmaceutical research. Phosphatase is classified based on substrate specificity, sequence homology, and optimal activity. Acid phosphatase and alkaline phosphatase are two phosphatase enzymes.

CONTENTS

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

 What is Acid Phosphatase?

Acid phosphatase is a phosphatase enzyme that is optimally active in an acidic pH. It is an enzyme used to release attached phosphoryl groups from molecules during digestion. It can also be further classified as a phosphomonoesterase. Acid phosphatase is stored in lysosomes. Acid phosphatase works when lysosomes fuse with endosomes. This is because lysosomes and endosomes are acidified while they are working. An acidic environment is highly important for the function of the acid phosphatase enzyme.

Acid phosphatase is present in many animal and plant species. In humans, different forms of acid phosphatase are found in different organs. Their serum levels are used to evaluate the success of the surgical treatment of prostate cancer. Acid phosphatase was also used in the past to diagnose prostate cancer. Furthermore, it is also used as a cytogenetic marker to differentiate two lineages of acute lymphoblastic leukemia (ALL): B-ALL and T-ALL.

Soil microorganisms use acid phosphatase to obtain organically bound phosphate nutrients. Some plant roots discharge carboxylates that perform the function of phosphatase. Therefore, this enzyme helps plants to mobilize phosphorous in nutrient-deficient soils. Moreover, Norcardia bacterial species degrade acid phosphatase enzyme and use it as a carbon source.

What is Alkaline Phosphatase?

Alkaline phosphatase is a phosphatase enzyme that is optimally active in an alkaline pH. It is a homodimeric protein enzyme of 86 kDa. Each monomer contains five cysteine residues, two zinc atoms, and one magnesium atom, which are extremely important for the catalytic function of alkaline phosphatase. It has the ability to dephosphorylate compounds. This enzyme is found in both prokaryotes as well as eukaryotes. However, different structural forms exist depending on the environment these organisms live in.

In humans, it plays a vital role in metabolism within the liver and development within the skeleton. Therefore, its concentration in the bloodstream can be used as a biomarker to diagnose hepatitis and osteomalacia. Abnormal levels of alkaline phosphatase could also indicate issues pertaining to liver, gall bladder, or bone. Moreover, conditions such as kidney tumors, infection and malnutrition also have shown an abnormal level of alkaline phosphatase in blood. Alkaline phosphatase level in the blood is determined through the ALP test.

What are the Similarities Between Acid Phosphatase and Alkaline Phosphatase?

• Acid phosphatase and alkaline phosphatase are two types of phosphatase enzymes.
• Both are proteins made up of amino acids.
• They are hydrolases.
• Both have the function of dephosphorylating compounds.
• They are present in prokaryotes as well as eukaryotes.

What is the Difference Between Acid Phosphatase and Alkaline Phosphatase?

Acid phosphatase is a phosphatase enzyme that is optimally active in an acidic pH, while alkaline phosphatase is a phosphatase enzyme that is optimally active in an alkaline pH. So, this is the key difference between acid phosphatase and alkaline phosphatase. Furthermore, acid phosphatase is a 35 kDa protein, while alkaline phosphatase is a 86 kDa protein.

The below infographic lists the differences between acid phosphatase and alkaline phosphatase in tabular form for side by side comparison.

Summary – Acid Phosphatase vs Alkaline Phosphatase

Phosphatase enzyme hydrolyzes phosphoric acid monoester into a phosphate ion and an alcohol. Acid phosphatase and alkaline phosphatase are two types of phosphatase enzymes. Acid phosphatase functions optimally in acidic pH, while alkaline phosphatase functions optimally in alkaline pH. Thus, this is the key difference between acid phosphatase and alkaline phosphatase.

Reference:

1. “Acid Phosphatase.” An Overview | ScienceDirect Topics.
2. Sharma, Ujjawal, et al. “Alkaline Phosphatase: An Overview.” Indian Journal of Clinical Biochemistry : IJCB, Springer India, July 2014.

Image Courtesy:

1. “Space filling representation for ACP 6” By Karlwess – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “PLAP 1ZEF dimer” By E A S – Own work (CC BY-SA 3.0) via Commons Wikimedia