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Ptyalin

Alpha-amylase
Salivary alpha-amylase 1SMD.png
Human salivary amylase: calcium ion visible in pale khaki, chloride ion in green. PDB 1SMD
Identifiers
EC number 3.2.1.1
CAS number 9000-90-2
Databases
IntEnz IntEnz view
BRENDA BRENDA entry
ExPASy NiceZyme view
KEGG KEGG entry
MetaCyc metabolic pathway
PRIAM profile
PDB structures RCSB PDB PDBe PDBsum
Alpha-amylase catalytic domain
PDB 1cyg EBI.jpg
Cyclodextrin glucanotransferase (e.c.2.4.1.19) (cgtase)
Identifiers
Symbol Alpha-amylase
Pfam PF00128
Pfam clan CL0058
InterPro IPR006047
SCOP 1ppi
SUPERFAMILY 1ppi
OPM superfamily 125
OPM protein 1wza
CAZy GH13
Alpha-amylase C-terminal beta-sheet domain
PDB 1rp8 EBI.jpg
Crystal structure of barley alpha-amylase isozyme 1 (amy1) inactive mutant d180a in complex with maltoheptaose
Identifiers
Symbol Alpha-amyl_C2
Pfam PF07821
InterPro IPR012850
Alpha amylase, C-terminal all-beta domain
PDB 5cgt EBI.jpg
maltotriose complex of preconditioned cyclodextrin glycosyltransferase mutant
Identifiers
Symbol Alpha-amylase_C
Pfam PF02806
Pfam clan CL0369
InterPro IPR006048
SCOP 1ppi
SUPERFAMILY 1ppi

α-Amylase is a protein enzyme EC 3.2.1.1 that hydrolyses alpha bonds of large, alpha-linked polysaccharides, such as starch and glycogen, yielding glucose and maltose. It is the major form of amylase found in humans and other mammals. It is also present in seeds containing starch as a food reserve, and is secreted by many fungi.

Although found in many tissues, amylase is most prominent in pancreatic juice and saliva, each of which has its own isoform of human α-amylase. They behave differently on isoelectric focusing, and can also be separated in testing by using specific monoclonal antibodies. In humans, all amylase isoforms link to chromosome 1p21 (see AMY1A).

Amylase is found in saliva and breaks starch into maltose and dextrin. This form of amylase is also called "ptyalin" /ˈtəlɪn/ It will break large, insoluble starch molecules into soluble starches (amylodextrin, erythrodextrin, and achrodextrin) producing successively smaller starches and ultimately maltose. Ptyalin acts on linear α(1,4) glycosidic linkages, but compound hydrolysis requires an enzyme that acts on branched products. Salivary amylase is inactivated in the stomach by gastric acid. In gastric juice adjusted to pH 3.3, ptyalin was totally inactivated in 20 minutes at 37 °C. In contrast, 50% of amylase activity remained after 150 minutes of exposure to gastric juice at pH 4.3. Both starch, the substrate for ptyalin, and the product (short chains of glucose) are able to partially protect it against inactivation by gastric acid. Ptyalin added to buffer at pH 3.0 underwent complete inactivation in 120 minutes; however, addition of starch at a 0.1% level resulted in 10% of the activity remaining, and similar addition of starch to a 1.0% level resulted in about 40% of the activity remaining at 120 minutes.


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Wikipedia

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