Oxidation states, carbohydrate derivatives

This chapter, therefore, ends the monograph with a potpourri of reactions all of which occur without a change in oxidation state. In many cases, the reaction is one of nucleophilic attack at an electrophilic C-atom. The result is often hydrolytic bond cleavage (e.g., in carbohydrate conjugates, disubstitut-ed methylene and methine groups, imines, oximes, isocyanates, and nitriles, and various ring systems) or a nucleophilic substitution (e.g., hydrolytic de-halogenation of halocarbons and chloroplatin derivatives, and cyclization reactions). The formation of multiple bonds by dehydration is a special case to be discussed separately. 

FIGURE 2.2 Carbohydrate derivatives with different oxidation states. 

FIGURE 4 8 Oxidation of carbohydrate and fatty adds for the production of energy. In the resting state, glycogen in the liver is broken down to glucose units however, both liver (kft) and muscle (right) derive most of their energy from fatty acids released from adipose tissue into the bloodstrecim and oxidized via the Krebs cycle. When carbohydrate is oxidized in the liver, it tends to be released into the bloodstream as pyruvate and lactate. 

Enzymes that contain carbohydrate, such as HRP or GO, may be oxidized with periodate to create reactive derivatives that subsequently can be used to label antibodies or other targeting molecules at their amine groups. The aldehyde-HRP intermediate may be stored for extended periods in a frozen or lyophilized state without loss of activity (either enzymatic or coupling potential). Avoid, however, storage in a liquid state, since polymerization may occur—resulting in precipitation and loss of activity. 

Ceruloplasmin. This is the most well-known and yet the least understood copper protein. It is an a2-globulin and there is conclusive evidence that this 132000 molecular weight glycoprotein has just one polypeptide chain [9]. It has 7% carbohydrate. It contains six atoms of copper per molecule. Copper in ceruloplasmin exists in both cupric and cuprous forms. Partial removal of copper from ceruloplasmin results in the loss of its characteristic blue color and loss of enzymatic activity. Ceruloplasmin has enzymatic oxidase activity toward several substrates at pH 5.4-S.9. The best substrate is p-phenylenediamine or its dimethyl derivative. Ceruloplasmin can oxidize ferrous ion to ferric ion. The ceruloplasmin level in the newborn is less than 10 mg/100 mL serum. It rises to adult levels (30.4 5 mg/lOO mL) by 2-4 months of age and continues to rise to a peak at 2-3 years and this declines to adult levels by 12 years of age. The level of ceruloplasmin is affected by various pathological states. Usually, a pronounced deficiency of this protein in serum is characteristic of both Wilson s and Menkes s diseases although normal levels have also been reported in the case of Wilson s disease. 

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