Abstract
The β-amylase limit dextrins of glycogen and amylopectin are completely debranched by joint action of isoamylase and pullulanase. Action of isoamylase alone results in incomplete debranching as a consequence of the inability of this enzyme to hydrolyze those A-chains that are two glucose units in length (half the total number of A-chains). From the reducing powers released by isoamylase acting (a) alone and (b) in conjunction with pullulanase, the relative numbers of A- (unsubstituted) and B- (substituted) chains in the β-dextrins, and therefore in the native polysaccharides themselves, can be calculated. Examination of a series of glycogens and amylopectins in this way showed that the ratio of A-chains: B-chains is markedly higher in amylopectins (1.5-2.6:1) than in glycogens (0.6-1.2:1). Glycogen typically contains A-chains and B-chains in approximately equal numbers; amylopectin typically contains approximately twice as many A-chains as B-chains. These polysaccharides therefore differ in degree of multiple branching as well as in average chain length. A consequence of these findings is that amylopectin cannot be formed in vivo by debranching of a glycogen precursor, as proposed by Erlander, since it is impossible to increase the A:B chain ratio by action of a debranching enzyme.
| Original language | English |
|---|---|
| Pages (from-to) | 234-238 |
| Number of pages | 5 |
| Journal | Archives of Biochemistry and Biophysics |
| Volume | 161 |
| Issue number | 1 |
| DOIs | |
| State | Published - Jan 1 1974 |
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ASJC Scopus subject areas
- Biochemistry
- Biophysics
- Molecular Biology
Cite this
Multiple branching in glycogen and amylopectin. / Marshall, J. J.; Whelan, William J.
In: Archives of Biochemistry and Biophysics, Vol. 161, No. 1, 01.01.1974, p. 234-238.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Multiple branching in glycogen and amylopectin
AU - Marshall, J. J.
AU - Whelan, William J.
PY - 1974/1/1
Y1 - 1974/1/1
N2 - The β-amylase limit dextrins of glycogen and amylopectin are completely debranched by joint action of isoamylase and pullulanase. Action of isoamylase alone results in incomplete debranching as a consequence of the inability of this enzyme to hydrolyze those A-chains that are two glucose units in length (half the total number of A-chains). From the reducing powers released by isoamylase acting (a) alone and (b) in conjunction with pullulanase, the relative numbers of A- (unsubstituted) and B- (substituted) chains in the β-dextrins, and therefore in the native polysaccharides themselves, can be calculated. Examination of a series of glycogens and amylopectins in this way showed that the ratio of A-chains: B-chains is markedly higher in amylopectins (1.5-2.6:1) than in glycogens (0.6-1.2:1). Glycogen typically contains A-chains and B-chains in approximately equal numbers; amylopectin typically contains approximately twice as many A-chains as B-chains. These polysaccharides therefore differ in degree of multiple branching as well as in average chain length. A consequence of these findings is that amylopectin cannot be formed in vivo by debranching of a glycogen precursor, as proposed by Erlander, since it is impossible to increase the A:B chain ratio by action of a debranching enzyme.
AB - The β-amylase limit dextrins of glycogen and amylopectin are completely debranched by joint action of isoamylase and pullulanase. Action of isoamylase alone results in incomplete debranching as a consequence of the inability of this enzyme to hydrolyze those A-chains that are two glucose units in length (half the total number of A-chains). From the reducing powers released by isoamylase acting (a) alone and (b) in conjunction with pullulanase, the relative numbers of A- (unsubstituted) and B- (substituted) chains in the β-dextrins, and therefore in the native polysaccharides themselves, can be calculated. Examination of a series of glycogens and amylopectins in this way showed that the ratio of A-chains: B-chains is markedly higher in amylopectins (1.5-2.6:1) than in glycogens (0.6-1.2:1). Glycogen typically contains A-chains and B-chains in approximately equal numbers; amylopectin typically contains approximately twice as many A-chains as B-chains. These polysaccharides therefore differ in degree of multiple branching as well as in average chain length. A consequence of these findings is that amylopectin cannot be formed in vivo by debranching of a glycogen precursor, as proposed by Erlander, since it is impossible to increase the A:B chain ratio by action of a debranching enzyme.
UR - http://www.scopus.com/inward/record.url?scp=0015994278&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=0015994278&partnerID=8YFLogxK
U2 - 10.1016/0003-9861(74)90256-2
DO - 10.1016/0003-9861(74)90256-2
M3 - Article
AN - SCOPUS:0015994278
VL - 161
SP - 234
EP - 238
JO - Archives of Biochemistry and Biophysics
JF - Archives of Biochemistry and Biophysics
SN - 0003-9861
IS - 1
ER -