Glycogen Types

T. Shimonaga, S. Fujiwara, M. Kaneko, A. Izumo, S. Nihei, P. B. Francisco, Jr., A. Satoh, N. Fujita, Y. Nakamura, and M. Tsuzuki, Variation in storage a-polyglucans of red algae Amylose and semi-amylopectin types in Porphyridium and glycogen type in Cyanidium, Mar. Biotechnol., 9 (2007) 192-202. 

In contrast to the above-mentioned protozoa which synthesize glycogen-type polysaccharides, certain ciliates (for example, Cycloposthium) contain an amylopectin-type of polysaccharide, whilst the flagellate Polytomella caeca stores a typical two-component starch. ... 

For the synthesis of glycogen-type polysaccharides from a-n-glucopyran-osyl phosphate, two enzymes are required. Phosphorylases, in presence of a suitable primer, synthesize linear chains of -( —> 4)-linked n-glucose residues these are then converted into a branched polysaccharide by a branching enzyme. ... 

The conversion of sucrose into a branched polysaccharide of the amylo-pectin-glycogen type by a bacterial-enzyme system was discovered by Hehre and his coworkers. Enzyme action involves the synthesis of polymeric chains of (1— 4)-linked a-D-glucose residues by a transglucosylase named amylosucrase, followed by the action of a branching enzyme. 

More recently, Erlander has proposed that amylopectin is synthesized from a glycogen-type precursor by means of a debranching enzyme, as yet undiscovered. The linear chains produced by debranching are then connected together to form amylose. This proposal will be considered in the next Section. 

Erlanderi has suggested an alternative theory, which accounts for the coexistence of a granular starch and a glycogen-type polysaccharide in sweet corn, and which is also applicable to all other plants. It is postulated that glycogen is synthesized first partial debranching then occurs, to yield amylopectin and short, linear chains of (1— 4)-linked a-D-glucose... 

Properties of Human-liver Glycogen, Type IV Glycogen, and Waxy-maize Amylopectin ... 

VII. Synthesis of Starch-Glycogen Type Polysaccharides by Transglucosidases 260... 

VII. SYNTHESIS OF STARCH-GLYCOGEN TYPE POLYSACCHARIDES BY TRANSGLUCOSIDASES... 

Eleven defects in the metabolism of glycogen have been reported nine of them affect skeletal muscle directly (see Figure 5), but only glycogenosis type II (acid maltase deficiency) and glycogenesis type V (myophosphorylase deficiency) are reasonably common the rest are rare and some have been recorded in isolated case studies only. 

Glycogenosis type IV (branching enzyme deficiency) results in the formation of a variant of glycogen, characterized by abnormally long inner and outer glucosyl chains and fewer branch points than normal. The abnormal variant is stored in sufficient amounts to cause some vacuolation. The clinical manifestations of this... 

Glycogenosis type VIII (phosphorylase b kinase deficiency) gives rise to myopathy and liver disease, either singly or in combination. Phosphorylase b kinase (PBK) converts the inactive b form of both muscle and liver phosphorylases to the active a forms of the enzymes. The ischemic lactate test sometimes shows a flat result as in McArdle s disease, but is more likely to be normal. Histochemical demonstration of myophosphorylase activity in tissue sections shows a near-normal reaction due to the presence of phosphorylase a. Accumulation of glycogen is modest and found mainly in type 2 (fast-twitch glycolytic) muscle fibers. 

Glycogen storage disease is a generic term to describe a group of inherited disorders characterized by deposition of an abnormal type or quantity of glycogen in the tissues. The principal glycogenoses are summarized in Table 18—2. Deficiencies of adenylyl kinase and cAMP-dependent protein kinase have also been re-... 

Type 1 Von Gierke s disease Deficiency of glucose-6-phosphatase Liver cells and renal tubule cells loaded with glycogen. Hypoglycemia, lactic-acidemia, ketosis, hyperlipemia. 

Type II Pompe s disease Deficiency of lysosomal a-1 4- and 1 ->6-glucosldase (acid maltase) Fatal, accumulation of glycogen in lyso-somes, heart failure. 

Type VI Hers disease Deficiency of liver phosphorylase High glycogen content in liver, tendency toward hypoglycemia. 

There are important methodologic considerations which apply to the use of cultured amniotic fluid cells for the detection of biochemical disorders. The first is that the enzymes which can be sampled are those which are usually present in fibroblasts or fibroblast-like cells. Therefore, conditions such as phenylketonuria and glycogen storage disease type I, which are associated with deficiencies of enzymes present only in liver and kidney, are not amenable to this approach. The same also pertains to enzyme deficiencies affecting other specific tissues. 

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