Pectate lyase () is an enzyme involved in the maceration and soft rotting of plant tissue. Pectate lyase is responsible for the eliminative cleavage of
pectate
Pectic acid, also known as polygalacturonic acid, is a water-insoluble, transparent gelatinous acid existing in over-ripe fruit and some vegetables. It is a product of pectin degradation in plants, and is produced via the interaction between pecti ...
, yielding oligosaccharides with 4-deoxy-α-D-mann-4-enuronosyl groups at their non-reducing ends. The protein is maximally expressed late in pollen development. It has been suggested that the pollen expression of pectate lyase genes might relate to a requirement for pectin degradation during pollen tube growth.
This
enzyme
Enzymes () are proteins that act as biological catalysts by accelerating chemical reactions. The molecules upon which enzymes may act are called substrates, and the enzyme converts the substrates into different molecules known as products. A ...
catalyzes
Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...
the
chemical reaction
A chemical reaction is a process that leads to the IUPAC nomenclature for organic transformations, chemical transformation of one set of chemical substances to another. Classically, chemical reactions encompass changes that only involve the pos ...
:Eliminative cleavage of (1→4)-α-D-galacturonan to give oligosaccharides with 4-deoxy-α-D-galact-4-enuronosyl groups at their non-reducing ends
The structure and the folding kinetics of one member of this family, pectate lyase C (''pelC'')1 from Erwinia chrysanthemi has been investigated in some detail,. PelC contains a parallel beta-helix folding motif. The majority of the regular secondary structure is composed of parallel beta-sheets (about 30%). The individual strands of the sheets are connected by unordered loops of varying length. The backbone is then formed by a large helix composed of beta-sheets. There are two disulphide bonds in PelC and 12
proline
Proline (symbol Pro or P) is an organic acid classed as a proteinogenic amino acid (used in the biosynthesis of proteins), although it does not contain the amino group but is rather a secondary amine. The secondary amine nitrogen is in the prot ...
residues. One of these prolines, Pro220, is involved in a ''cis'' peptide bond. The folding mechanism of PelC involves two slow phases that have been attributed to proline isomerization.
Some of the proteins in this family are
allergen
An allergen is a type of antigen that produces an abnormally vigorous immune response in which the immune system fights off a perceived threat that would otherwise be harmless to the body. Such reactions are called allergies.
In technical terms ...
s. Allergies are hypersensitivity reactions of the immune system to specific substances called allergens (such as pollen, synthetic materials, dust, stings, drugs, or food) that, in most people, result in no symptoms. A nomenclature system has been established for antigens (allergens) that cause IgE-mediated atopic allergies in humans.WHO/IUIS Allergen Nomenclature Subcommittee (King TP, Hoffmann D, Loewenstein H, Marsh DG, Platts-Mills TAE, Bull TW). World Health Organ. 72:797–806 (1994). This nomenclature system is defined by a designation that is composed of the first three letters of the genus; a space; the first letter of the species name; a space and an Arabic number. In the event that two species names have identical designations, they are discriminated from one another by adding one or more letters (as necessary) to each species designation.
The allergens in this family include allergens with the following designations: ''Amb a'' 1, ''Amb a'' 2, ''Amb a'' 3, ''Cha o'' 1, ''Cup a'' 1, ''Cry j'' 1, ''Jun a'' 1.
Two of the major allergens in the pollen of short ragweed (''
Ambrosia artemisiifolia
''Ambrosia artemisiifolia'', with the common names common ragweed, annual ragweed, and low ragweed, is a species of the genus '' Ambrosia'' native to regions of the Americas.
Taxonomy
The species name, ''artemisiifolia'', is given because the le ...
'') are Amb a I and Amb a II. The primary structure of Amb a II has been deduced and has been shown to share ~65% sequence identity with the Amb a I multigene family of allergens. Members of the ''Amb a'' I/''a'' II family include ''
Tobacco
Tobacco is the common name of several plants in the genus '' Nicotiana'' of the family Solanaceae, and the general term for any product prepared from the cured leaves of these plants. More than 70 species of tobacco are known, but the ...
'' (''Nicotiana tabacum'', Common tobacco) pectate lyase, which is similar to the deduced amino acid sequences of two pollen-specific pectate lyase genes identified in ''
Lycopersicon esculentum
The tomato is the edible berry of the plant ''Solanum lycopersicum'', commonly known as the tomato plant. The species originated in western South America, Mexico, and Central America. The Mexican Nahuatl word gave rise to the Spanish word , ...
'' (Tomato); ''Cry j'' I, a major allergenic glycoprotein of ''
Cryptomeria japonica
''Cryptomeria'' (literally "hidden parts") is a monotypic genus of conifer in the cypress family Cupressaceae, formerly belonging to the family Taxodiaceae. It includes only one species, ''Cryptomeria japonica'' ( syn. ''Cupressus japonica'' L ...
'' (Japanese cedar)—the most common pollen allergen in Japan; and P56 and P59, which share sequence similarity with pectate lyases of plant pathogenic bacteria.
This enzyme belongs to the family of
lyase
In biochemistry, a lyase is an enzyme that catalyzes the breaking (an elimination reaction) of various chemical bonds by means other than hydrolysis (a substitution reaction) and oxidation, often forming a new double bond or a new ring structure. ...
s, specifically those carbon-oxygen lyases acting on polysaccharides. The
systematic name A systematic name is a name given in a systematic way to one unique group, organism, object or chemical substance, out of a specific population or collection. Systematic names are usually part of a nomenclature.
A semisystematic name or semitrivial ...
of this enzyme class is (1->4)-alpha-D-galacturonan lyase. Other names in common use include polygalacturonic transeliminase, pectic acid transeliminase, polygalacturonate lyase, endopectin methyltranseliminase, pectate transeliminase, endogalacturonate transeliminase, pectic acid lyase, pectic lyase, acid lyase, PGA lyase, PPase-N, endo-alpha-1,4-polygalacturonic acid lyase, polygalacturonic acid lyase, pectin trans-eliminase, and polygalacturonic acid trans-eliminase. This enzyme participates in