207
Effect of Cadmium Pentose Phosphate Pathway
Pentose phosphate pathway consists of two steps, the first step is the oxidative production of NADPH and the second step is non-oxidative inter-conversion of sugar
[22]. Pentose phosphate pathway is a biochemical process that is parallel to glycolysis and it is a vital source for the production of NADPH [23]. In the process of
glycolysis, glucose-6-phosphate is produced on which glucose-6-phosphate dehydrogenase converts it into 6-phosphogluconate. In this process, NADPH is produced
which is used to maintain the level of glutathione in a reduced form whose function
to kill the oxidative metabolites that are dangerous [24]. Cadmium has great potential to decrease the level of glutathione by inhibiting the activity of glucose-6phosphate dehydrogenase (Fig. 13.2). The decreased activity of glucose-6-phosphate
dehydrogenase may cause the induction of diabetes mellitus due to the oxidative
stress-induced by oxidation [25]. The studies also show that the production of
glucose- 6-phosphate is decreased due to inhibition of hexokinase, an enzyme
involved in glycolysis, and pentose phosphate pathway suppressed due to reduced
level of glucose-6-phosphate [26].
Effect of Cadmium Glycogenolysis
In the process of glycogenolysis, glycogen is phosphorylated by glycogen phosphorylase and as a result, glucose-1-phosphate is produced. Glucose-1-phosphate is
converted into glucose-6-phosphate and this reaction is catalyzed by an enzyme
Fig. 13.2 Schematic representation of the mechanism of cadmium and arsenic interfering with
enzymes that are involved in carbohydrates metabolism. Adopted from [12]. GP glycogen phosphorylase, GS glycogen synthetase, UDP uridine diphosphate glucose, PGM phosphoglucomutase, HK hexokinase, G6Pase glucose-6-phosphatase, PFK phosphofructokinase, FBase
fructose-1,6-bisphosphatase, PK pyruvate kinase, PC pyruvate carboxylase, PEPC phosphoenolpyruvate carboxykinase, G6PDH glucose-6-phosphate dehydrogenase, NADP nicotinamide adenine dinucleotide phosphate, GSH glutathione
13 Role of Heavy Metals in Metabolic Disorders
Effect of Cadmium Pentose Phosphate Pathway
Pentose phosphate pathway consists of two steps, the first step is the oxidative production of NADPH and the second step is non-oxidative inter-conversion of sugar
[22]. Pentose phosphate pathway is a biochemical process that is parallel to glycolysis and it is a vital source for the production of NADPH [23]. In the process of
glycolysis, glucose-6-phosphate is produced on which glucose-6-phosphate dehydrogenase converts it into 6-phosphogluconate. In this process, NADPH is produced
which is used to maintain the level of glutathione in a reduced form whose function
to kill the oxidative metabolites that are dangerous [24]. Cadmium has great potential to decrease the level of glutathione by inhibiting the activity of glucose-6phosphate dehydrogenase (Fig. 13.2). The decreased activity of glucose-6-phosphate
dehydrogenase may cause the induction of diabetes mellitus due to the oxidative
stress-induced by oxidation [25]. The studies also show that the production of
glucose- 6-phosphate is decreased due to inhibition of hexokinase, an enzyme
involved in glycolysis, and pentose phosphate pathway suppressed due to reduced
level of glucose-6-phosphate [26].
Effect of Cadmium Glycogenolysis
In the process of glycogenolysis, glycogen is phosphorylated by glycogen phosphorylase and as a result, glucose-1-phosphate is produced. Glucose-1-phosphate is
converted into glucose-6-phosphate and this reaction is catalyzed by an enzyme
Fig. 13.2 Schematic representation of the mechanism of cadmium and arsenic interfering with
enzymes that are involved in carbohydrates metabolism. Adopted from [12]. GP glycogen phosphorylase, GS glycogen synthetase, UDP uridine diphosphate glucose, PGM phosphoglucomutase, HK hexokinase, G6Pase glucose-6-phosphatase, PFK phosphofructokinase, FBase
fructose-1,6-bisphosphatase, PK pyruvate kinase, PC pyruvate carboxylase, PEPC phosphoenolpyruvate carboxykinase, G6PDH glucose-6-phosphate dehydrogenase, NADP nicotinamide adenine dinucleotide phosphate, GSH glutathione
13 Role of Heavy Metals in Metabolic Disorders