Branching enzyme deficiency

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... 

In glycogenosis type III (debranching enzyme deficiency) the absorption maximum is around 410 nm in muscle in liver the maximum remains around 460 nm, but there is a pronounced shoulder at 410 nm. In glycogenosis type IV (branching enzyme deficiency) the absorption maximum is around 530 nm. 

Genetic Studies on Branching Enzyme-Deficient Mutants... 

Glycogen Storage Disease Type IV Branching Enzyme Deficiency. 304... 

Table 15.11. Glycogen storage disease type 4 (branching enzyme deficiency) ...

Bifunctional protein deficiency. The enzyme defect involves the D-bifunctional protein. This enzyme contains two catalytic sites, one with enoyl-CoA hydratase activity, the other with 3-hydroxyacyl-CoA activity [13]. Defects may involve both catalytic sites or each separately. The severity of clinical manifestations varies from that of a very severe disorder that resembles Zellweger s syndrome clinically and pathologically, to somewhat milder forms. Table 41-6 shows that biochemical abnormalities involve straight chain, branched chain fatty acids and bile acids. Bifunctional deficiency is often misdiagnosed as Zellweger s syndrome. Approximately 15% of patients initially thought to have a PBD have D-bifunctional enzyme deficiency. Differential diagnosis is achieved by the biochemical studies listed in Table 41-7 and by mutation analysis. 

Fig. 5.1.2 Cholesterol biosynthesis branch of the isoprenoid biosynthetic pathway. Enzymes are numbered as follows 1 squalene synthase 2 squalene epoxidase 3 2,3-oxidosqua-lene sterol cyclase 4 sterol A24-reductase (desmosterolosis) 5 sterol C-14 demethylase 6 sterol A14-reductase (hydrops-ectopic calcification-moth-eaten, HEM, dysplasia) 7 sterol C-4 demethylase complex (including a 3/ -hydroxysteroid dehydrogenase defective in congenital hemidyspla-sia with ichthyosiform nevus and limb defects, CHILD, syndrome) 8 sterol A8-A7 isomerase (Conradi-Hunermann syndrome CDPX2) 9 sterol A5-desaturase (lathosterolosis) 10 sterol A7-reductase (Smith-Lemli-Opitz syndrome). Enzyme deficiencies are indicated by solid bars across the arrows...

Enzymes Involved in Starch Biosynthesis. Much of the eady data dealing with starch biosynthesis in plants are derived from the study of various mutants. The shrunken-2 and britde-2 mutants of maize have gready reduced levels of ADPGPP activity owing to the absence of one of the two subunits of this enzyme, and result in a shrunken seed appearance. Mendel s eady work on inheritance of traits was performed with a pea mutant deficient in branching enzyme activity (61). Mutations in plants affecting starch biosynthesis can have severe results to plant morphology and viability. 

Guan H. P., Kuriki, T., Sivak, M., and Preiss, J. 1995. Maize branching enzyme catalyzes synthesis of glycogen-like polysaccharide in glgB-deficient Escherichia coli. Proc. Natl. Acad. Science USA 92, 964-967. 

C-1) Deficiency of branching enzyme (lype IV GSD Anderson Disease). Here the liver jiroduces an abnormal giycGfeea with veiy long chains. Tliere is aik... 

---