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What is a Lyase?

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In physiology, Lyase meaning is defined as any member of an enzyme class that catalyzes the removal or addition of the elements of ammonia (nitrogen, hydrogen), carbon dioxide (carbon, oxygen), or water (oxygen, hydrogen) at double bonds. For example, dehydrases remove water. And decarboxylases remove carbon dioxide from amino acids.


The systematic names can be formed as "substrate group-lyase." Common names are aldolase, dehydratase, decarboxylase, and so on. Synthase may be used in the name of a product when it is very essential, such as phosphosulfolactate synthase (EC, sulfite's Michael addition to phosphoenolpyruvate). A combination of both a Michael and elimination addition is seen in the O-succinylhomoserine (thiol) -lyase (either MetY or MetZ) that catalyze first the γ-elimination of O-succinylhomoserine (succinate as a leaving group) and after that, the sulfide addition to the vinyl intermediate. First, this particular reaction was classified as a lyase (EC, but then, it was reclassified as a transferase (EC

Examples of Lyase

A few examples of lyase include phenylalanine ammonia lyase, citrate lyase, isocitrate lyase, hydroxynitrile, pectate lyase, argininosuccinate lyase, pyruvate formate lyase, alginate lyase, and pectin lyase.


In the classification of EC number of enzymes, EC 4 could represent lyases that may be classified further into seven subclasses.

  1. Lyases, in the EC 4.1 cleave carbon-carbon bonds and also include decarboxylases (EC 4.1.1), aldehyde lyases (EC 4.1.2) by facilitating the aldol condensation's reverse reaction, oxo acid lyases (EC 4.1.3), which catalyzes the cleavage of several 3-hydroxy acids, including others (EC 4.1.99).

  2. EC 4.2 has a group of lyases, which break carbon-oxygen bonds like dehydratases. Hydro-lyases, being a part of carbon-oxygen lyases, may facilitate the cleavage of C-O bonds by water elimination. Phosphate reduction or the removal of alcohol from a polysaccharide was promoted by a few other carbon-oxygen lyases.

  3. Lyases cleaving the carbon-nitrogen bonds are sorted as EC 4.3. And, they could release ammonia with the powerful cleaving ability and simultaneously produce a double ring or bond. A few of these enzymes may also help to eliminate an amide or amine group.

  4. EC 4.4 shows lyases that split carbon-sulfur bonds that could either substitute or eliminate dihydrogen sulfide (H2S) from a reaction.

  5. Carbon-halide bonds, by cleaving enzymes, are the lyases in EC 4.5 and which utilize an action mode, which removes hydrochloric acid from dichloro-diphenyl-trichloroethane (DDT), a synthetic pesticide.

  6. EC 4.6 comprises the bonds of lyases fracturing phosphorus-oxygen, such as guanylyl cyclase and adenylyl cyclase, and they eliminate diphosphate from the nucleotide triphosphates.

  7. EC 4.99 is classified as part of a category of lyases.

Substrate Specificity

Usually, the specificity of a narrow substrate is considered to be a drawback for enzyme's commercialization in that it greatly restricts the enzyme's flexibility as an assistant in the related compound's production. Generally, lyases, but not all the time, are found with narrow substrate specificity. Most of the ammonia and hydratases-lyases indeed possess a quite narrow substrate specificity, whereas the substrate specificity for decarboxylases, oxynitrilases, and aldolases is much broader.

Here, it is noteworthy, the substrate specificity of a particular lyase varies based on its source. However, it is not given as an absolute prerequisite for enzymes to own the unrestricted substrate specificity for their commercial exploitation. Also, there are many lyases in the commercial use bearing a narrow substrate spectrum rather.

Cofactor Requirements

The enzyme's commercial potential may be severely limited by the expensive cofactor's requirement. Since the addition catalyzed by lyase does not implicate the mere reduction or oxidation, it is not an important requirement for cofactors. However, till now, many lyases identified do require cofactors that are involved in the stabilization of reaction intermediates, substrate binding, substrate polarization, temporary binding of the nucleophile, and more.

The majority of these cofactors are covalently bound to the enzyme and are not much expensive. Thereby, the lyases' cofactors do not establish a barrier to their commercialization. The requirements for lyases' cofactors differ as per their different sources.

Lyase Deficiency Disorder

Lyase deficiency, which is also referred to as HMG-CoA lyase deficiency, is given as a rare inherited disorder, which causes a mess in the metabolism of amino acid leucine and also prevents the body from synthesizing ketones, which are used for energy production during the body's food lacking periods. This condition could be inherited in an autosomal recessive pattern, which means that both copies of the gene in every cell undergo mutations.

Usually, the lyase deficiency symptoms express within the life's first year and primarily include vomiting, diarrhoea, dehydration, lethargy, and weak muscular development. During the lyase deficiency episode, blood sugar concentrations may be either extremely low or hypoglycemic and a few harmful compounds would be accumulated to cause the blood to becomes quite acidic.

Whereas, if it is left untreated, the disorder even could initiate convulsions, coma, breathing problems, and also death. Infection, strenuous exercise and other physical stresses may probably give rise to bouts with the symptoms of lyase deficiency.

FAQ (Frequently Asked Questions)

1. How to Relieve Lyase Deficiency Disorder?

Answer: The lyase deficiency symptoms would be amplified after going long periods with no food ingestion. Thus, people attacked with this specific disease should be ensured with regular ingestion and good balance. Intaking foods that are low in protein, rich in carbohydrates and fat may be beneficial to prevent low blood sugar levels. In addition, L-Carnitine can aid in the production of cellular energy, which would be extremely beneficial when the body is dehydrated and lethargic.

2. Explain Hydrolases with an Example?

Answer: Hydrolases is the one that split the molecule by addition of water. Examples of Hydrolase are: sucrose can be hydrolyzed into both glucose and fructose by adding water in the presence of enzyme sucrase.

3. What are Hydrolases?

Answer: Hydrolase is defined as a class of an enzyme that commonly performs as biochemical catalysts that use water in a chemical bond breakage that typically results in dividing a larger molecule into smaller molecules.

4. Explain Lyases with an Example?

Answer: Lyases will split the molecule without the addition of water. For example, aldolase A splits fructose-1 and 6-bisphosphate into dihydroxyacetone phosphate and glyceraldehyde-3- phosphatase without adding any water.