Pathway Tools
Intro Tutorial
discounted registration ends Sept 5, 2015 (Sat)
Pathway Tools
Intro Tutorial
discounted registration ends Sept 5, 2015 (Sat)
Pathway Tools
Intro Tutorial
discounted registration ends Sept 5, 2015 (Sat)
Pathway Tools
Intro Tutorial
discounted registration ends Sept 5, 2015 (Sat)
Pathway Tools
Intro Tutorial
discounted registration ends Sept 5, 2015 (Sat)
twitter

MetaCyc Compound Class: α-amylose

Synonyms: an α-amylose

Superclasses: all carbohydrates a carbohydrate a glycan a polysaccharide a glucan a linear alpha-D-glucan a 1,4-alpha-D-glucan
all carbohydrates a carbohydrate a glycan a polysaccharide a glucan starch

Summary:
Starch is a mixture of the two polymeric carbohydrates (polysaccharides) α-amylose and amylopectin.

α-Amylose contains up to several thousand glucosyl units linked almost exclusively in linear α(1->4) linkages, with very few branches of α(1->6) linkages. In amylopectin, on the other hand, branching is common, and occurs approximately every 24-30 glucose units.

α-Amylose accounts for 30% of starch, while amylopectin accounts for the other 70%.

α-amylose compound structure

Reactions known to consume the compound:

glycogen degradation III (via anhydrofructose) :
a 1,4-α-D-glucan → n 1,5-anhydro-D-fructose + β-D-glucopyranose

Not in pathways:
(1,4-α-D-glucosyl)(n) + H2O → (1,4-α-D-glucosyl)(n-1) + D-glucopyranose
a 1,4-α-D-glucan + H2O → a 1,4-α-D-glucan + maltose
sucrose + (1,4-α-D-glucosyl)(n) → D-fructofuranose + (1,4-α-D-glucosyl)(n+1)
a 1,4-α-D-glucan + n H2O → n a 1,4-α-D-glucan
a 1,4-α-D-glucan + n H2O → a 1,4-α-D-glucan + n maltotetraose
a 1,4-α-D-glucan + H2O → a 1,4-α-D-glucan + maltotriose
a 1,4-α-D-glucan + H2O → a 1,4-α-D-glucan + maltohexaose
a 1,4-α-D-glucan[periplasmic space] + n H2O[periplasmic space]a 1,4-α-D-glucan[periplasmic space] + maltohexaose[periplasmic space]

starch degradation II :
starch[chloroplast stroma] + n ATP[chloroplast stroma] + n H2O[chloroplast stroma] → a 6-phosphogluco-amylopectin[chloroplast stroma] + n AMP[chloroplast stroma] + n phosphate[chloroplast stroma]

starch degradation III , starch degradation IV :
starch[extracellular space] → a cyclodextrin[extracellular space]

starch degradation V :
starch[extracellular space] + H2O[extracellular space] → a maltodextrin(n)[extracellular space] + maltose[extracellular space] + D-glucopyranose[extracellular space]

Not in pathways:
starch + n H2O → n α-maltose
starch + n H2O → a long-linear glucan
starch + n H2O → a large-branched glucan
starch + H2O → maltose + glucose

starch degradation II :
a glucan[chloroplast stroma] + maltotriose[chloroplast stroma]a glucan[chloroplast stroma] + D-glucopyranose[chloroplast stroma]

Reactions known to produce the compound:

cellulose and hemicellulose degradation (cellulolosome) :
a feruloyl-polysaccharide + H2O → ferulate + a polysaccharide + H+

Reactions known to both consume and produce the compound:

glycogen biosynthesis I (from ADP-D-Glucose) :
a 1,4-α-D-glucan ↔ a glycogen
ADP-α-D-glucose + (1,4-α-D-glucosyl)(n) ↔ ADP + (1,4-α-D-glucosyl)(n+1)

starch biosynthesis :
ADP-α-D-glucose + (1,4-α-D-glucosyl)(n) ↔ ADP + (1,4-α-D-glucosyl)(n+1)

Not in pathways:
(1,4-α-D-glucosyl)(n) + phosphate ↔ (1,4-α-D-glucosyl)(n-1) + α-D-glucopyranose 1-phosphate

In Reactions of unknown directionality:

starch biosynthesis :
ADP-α-D-glucose[chloroplast stroma] + n (1,4-α-D-glucosyl)(n)[chloroplast stroma] = ADP[chloroplast stroma] + n α-amylose[chloroplast stroma]
n α-amylose = n amylopectin + n H2O
n amylopectin + α-amylose = n starch

starch biosynthesis :
n a 1,4-α-D-glucan = a (1,6)-α-D-glucosyl-(1,4)-α-glucan highly branched + n H2O

Not in pathways:
a 1,4-α-D-glucan = a cyclodextrin
n a 1,4-α-D-glucan = n starch + n H2O
(1,4-α-D-glucosyl)(n) = (1,4-α-D-glucosyl)(n-1) + a (1,6)-α-D-glucosyl-(1,4)-α-glucan
a 1,4-α-D-glucan + a 1,4-α-D-glucan = a 1,4-α-D-glucan + a 1,4-α-D-glucan
α-maltose 1-phosphate + (1,4-α-D-glucosyl)(n-1) = (1,4-α-D-glucosyl)(n+1) + phosphate
a nucleoside diphosphate-glucose + a 1,4-α-D-glucan = a nucleoside diphosphate + a 1,4-α-D-glucan
(1,4-α-D-glucosyl)(n) + (1,6-α-D-glucosyl)(m) = (1,4-α-D-glucosyl)(n-1) + (1,6-α-D-glucosyl)(m+1)

starch degradation I :
starch = a linear malto-oligosaccharide

Not in pathways:
n a 1,4-α-D-glucan = n starch + n H2O

Not in pathways:
a linear α-D-glucan + sucrose = an alternan
a linear α-D-glucan + ATP + H2O = [phospho-α-glucan] + AMP + phosphate + 2 H+

This compound has been characterized as an alternative substrate of the following enzymes: α-amylase

Credits:
Revised 15-Mar-2013 by Caspi R , SRI International


Report Errors or Provide Feedback
Please cite the following article in publications resulting from the use of MetaCyc: Caspi et al, Nucleic Acids Research 42:D459-D471 2014
Page generated by SRI International Pathway Tools version 19.0 on Wed Sep 2, 2015, BIOCYC14B.