Importance of Studying Carbohydrate-Active Enzymes

Carbohydrate-active enzymes (CAZymes) facilitate the formation and break down of complex carbohydrates and glycoconjugates. Studying them gives insight into the biological processes in which they are involved.

Categorization of CAZymes

The different CAZymes are compiled into a database and classified into different groups based on their function. There are roughly 300 CAZymes that fall into the following categories: glycoside hydrolases, glycosyltransferases, polysaccharide lyases, carbohydrate esterases, and carbohydrate-binding modules.

Genome and functional analyses of CAZymes allows for their characterization into distinct categories. Further study of the CAZymes in respect to specific biological processes allow for relationships between the CAZyme type and the process to be made.

Study of CAZymes in Xylogenesis

As carbohydrate metabolism is a key feature of vascular plant architecture, it is important to study how CAZymes contribute to this metabolism. In plants, CAZymes are responsible for the synthesis, modification, and degradation of carbohydrate biopolymers (in particular cellulose and hemicellulose), as well as the differences in gene copy number. Previous studies have compared the diversity of CAZymes between plant species and discovered that Populus trichocarpa has a higher diversity compared to Arabidopsis thaliana, showing the vast diversity and variance of CAZymes across different species. There is also varied CAZyme expression when comparing cells from non-wood forming tissue (e.g. young leaves) to cells involved cellulose and hemicellulose synthesis.  

Genome-wide analysis of CAZyme in plants has been performed on many different species of plant including Physcomitrella patens, Selaginella moellendorffii, Brachypodium distachyon, etc. The analyses uncovered the number of CAZyme genes in each species, the number of CAZyme domains within proteins, and the categorization of each CAZyme discovered. These statistics can be used to better understand the metabolic processes within plants and draw comparisons between different species of plant.

Study of CAZymes in Plant Cell Wall and Storage Polysaccharide Degradation

In plant pathogens, CAZymes are involved in the degradation of the cell wall and storage compounds. A barrier to the colonization of plants by microorganisms is the cell wall, which is mainly composed of polysaccharides such as cellulose, hemicellulose, and pectin.

Oomycetes are part of the Stramenopiles family and are microorganisms that colonize plants. A phylogenetic analysis of 11 Oomycetes revealed the genetic relationship between each one and uncovered information on the CAZymes from each one, which allowed each Oomycete to be classified. The analysis discovered that the Pythium family of Oomycetes have a limited capability to degrade cellulose, which is sufficient enough to allow penetration into plant cell walls but not enough to provide complete digestion of cellulose. The Oomycetes studied also showed a great ability to degrade Cutin and Pectin. These findings made it clear that Oomycetes contain CAZymes that aid in their ability to degrade complex carbohydrates in plants.

Study of CAZymes in the Human Gut Microbiome

CAZymes play a crucial role in the breakdown of complex carbohydrates such as cellulose, glycan, starch, and glycogen into components that can be absorbed by the intestine epithelium. The human genome only encodes roughly 17 CAZymes types, the majority of the CAZymes that act within the intestines are encoded by the microflora present in the gut. One of them, Bacteroides thetaiotaomicron, encodes for approximately 260 CAZymes. The study of CAZymes in the microbiota will allow for better understanding of complex carbohydrate metabolism in humans, and diseases that occur when it goes wrong. Past research has also shown that individuals with different CAZyme profiles of their gut microbiomes are likely to have different carbohydrate metabolic capacities.

A previous study used partial least square analysis to analyze the gut microbiota of several volunteers in varied age groups. The analysis discovered that age affects the abundance, diversity, and function of CAZymes. Another analysis discovered that bacteria harboring 10 specific CAZyme families can act as a causative factor towards obesity.

Benefits of Studying cCarbohydrate-Active Enzymes

Studying CAZymes provides a lot of information. As many processes within biology require carbohydrate metabolism, this information can be applied to a vast number of areas within the scientific field. Studying CAZymes provides a method to categorize organisms that use CAZymes in their metabolism.

Researching more into CAZymes will provide more information on diseases, microorganisms, development, and certain metabolic processes. It is certain that this area of study will provide even more important and interesting discoveries in the future.

Further Reading

• All Carbohydrate-Active Enzyme Content
• What is the Carbohydrate-Active Enzyme Classification System?

Written by

Samuel Mckenzie

Sam graduated from the University of Manchester with a B.Sc. (Hons) in Biomedical Sciences. He has experience in a wide range of life science topics, including; Biochemistry, Molecular Biology, Anatomy and Physiology, Developmental Biology, Cell Biology, Immunology, Neurology  and  Genetics.