The key difference between allozyme isozyme and isoform is based on their form. While allozymes are different forms of enzymes present in different genes, isozymes are variants present in different alleles of the same gene, and isoforms are various forms of proteins arising from modifications.
Proteins are composed of amino acids. The Central Dogma plays an important role in the determination of the amino acid sequence. The majority of enzymes are composed of proteins and fulfil a lot of vital physiological functions. Enzymes have different variants based on the form that’s present in each species. These forms determine the species specificity of an enzyme.
CONTENTS
1. Overview and Key Difference
2. What is Allozyme
3. What is Isozyme
4. What is Isoform
4. Similarities Between Allozyme Isozyme and Isoform
5. Side by Side Comparison – Allozyme vs Isozyme vs Isoform in Tabular Form
6. Summary
What is an Allozyme?
Allozyme, also called alloenzyme, is a form of an enzyme variant present in alleles. It differs structurally among other allozymes that code for various alleles present in a particular locus. Allozymes generally perform the same function. They arise due to mutations such as point mutations or insertion-deletion in a coding sequence of a gene. Therefore, the structural differences are due to mutations and changes in the DNA sequences. Structural differences among allozymes are seen through capillary electrophoresis. Each allozyme has a different molecular size and electrical charge. Allozymes act as molecular markers to determine the history of the evolution of different species in a large population. Therefore, allozymes are used in gene mapping related species.
What is an Isozyme?
An isozyme, also known as an isoenzyme, is a form of an enzyme variant present in alleles. Isozymes are enzymes that codes for various genes at different loci. It differs structurally as it consists of different amino acid sequences. Therefore, they show various sizes and shapes.
Figure 01: Isozyme
Isozymes catalyze the same chemical reactions under different conditions. Therefore, they metabolize biochemical pathways. Isozymes act as biochemical markers to determine relationships between species in evolution. Therefore, isozymes also help in gene mapping. Isozymes are derived through gene duplication, polyploidization, and nucleic acid hybridization.
What is an Isoform?
Isoforms, also known as protein isoforms or protein variants, is a group of similar proteins. Isoform consists of multiple proteins similar in function which have similar, but not identical, amino acid sequences. Protein isoforms usually derive through post-transcriptional modification of the same gene.
Figure 02: Isoform
Alternative splicing and variable promoter usage are few examples of such post-transcriptional modifications. Therefore, it shows genetic differences, which results in biological diversity. Isoforms carry out similar or different functions depending on their origin. Isoform production provides a mechanism to specialize the characteristics in genes.
What are the Similarities Between Allozyme Isozyme and Isoform?
- Allozymes, isozyme and isoforms are proteins.
- They all carry out similar chemical reactions acting as biological catalysts.
- They all act as markers to determine the evolution of different species.
What is the Difference Between Allozyme Isozyme and Isoform?
Even though all three are proteins in nature, they have varied amino acid sequences. They have varied forms at the allelic levels, which make them different to one another. While allozymes and isozymes are based on enzyme differences, isoforms are related to proteins. Both isozymes and isoforms originate from a single gene, whereas allozymes originate from multiple genes. So, this is the key difference between allozyme isozyme and isoform.
The below infographic lists the differences between allozyme isozyme and isoform in tabular form.
Summary – Allozyme Isozyme vs Isoform
Allozyme, isozyme and isoform are proteins. Allozyme and isozyme are enzyme variants, whereas isoform is a group of proteins. All three determines genetic differences and the relationship in the biological diversity within species. Allozymes, isozymes, and isoforms catalyze chemical reactions. Thus, this summarizes the difference between allozyme isozyme and isoform.
Reference:
1. Gunning, Peter W, and Edna C Hardeman. “Isoforms: Fundamental Differences.” ELife, ELife Sciences Publications, Ltd, 1 Feb. 2018, Available here.
2. “Isozyme.” An Overview | ScienceDirect Topics, Available here.
3. “About: Alloenzyme.” DBPedia, Available here.
Image Courtesy:
1. “Isoenzyme1” By علاء – Own work (CC BY-SA 4.0) via Commons Wikimedia
2. “DNA alternative splicing” By National Human Genome Research Institute – (Public Domain) via Commons Wikimedia
