46
the small intestine. By the metabolic process, galactose is converted into galactose- 1phosphate which is then combined with uridine phosphoglucose to form uridine
diphosphogalactose and glucose-1-phosphate (G1P). The deficiency of each of
these enzymes results in disorders of galactose metabolism, galactosemia being the
most common and severe disorder among them [13]. Galactosemia results from the
failure in the metabolism of galactose [14]. It is an autosomal recessive disorder, and
has three forms depending upon the deficiency of an enzyme involved [10].
Classic Galactosemia
This disorder is the manifestation of deficiency of GALT enzyme which occurs
because of the gene mutations of the GALT enzyme, hence leading to the accumulation of metabolites of galactose metabolism that are galactitol and galactose-1phosphate [10]. Galactose-1-phosphate can accumulate in all tissues and inhibit
other enzymes too as phosphoglucomutase and glucose-6-phosphate dehydrogenase
[14]. Newborn infants with classic galactosemia show normal weight at birth but
their weight shows a decline as they start feeding [15]. Newborns with this disorder
are asymptomatic but as they are exposed to milk, life-threatening symptoms start
appearing which include difficulties in feeding, renal tubular dysfunction, hypoglycemia, hepatomegaly, vomiting, diarrhea, and cataracts. Speech difficulties, cognitive disabilities, visual perceptions, hypergonadotropic hypogonadism, and reduced
bone mass are the long-term complications [8]. The mortality rate of classic galactosemia is 1 in 40,000 to 60,000 newborns [15]. Immediate restriction of galactose
containing foods is a primary treatment of classic galactosemia. Instead of this, soy
milk, amino acids-based formulas, or formulas with other carbohydrate sources are
preferred [10].
Fig. 2.2 Schematic representation of the Leloir pathway of galactose metabolism. ATP adenosine
triphosphate, ADP adenosine diphosphate, UDP uridine diphosphate, PPi inorganic pyrophosphate, GALK galactokinase
H. Sharif et al.
the small intestine. By the metabolic process, galactose is converted into galactose- 1phosphate which is then combined with uridine phosphoglucose to form uridine
diphosphogalactose and glucose-1-phosphate (G1P). The deficiency of each of
these enzymes results in disorders of galactose metabolism, galactosemia being the
most common and severe disorder among them [13]. Galactosemia results from the
failure in the metabolism of galactose [14]. It is an autosomal recessive disorder, and
has three forms depending upon the deficiency of an enzyme involved [10].
Classic Galactosemia
This disorder is the manifestation of deficiency of GALT enzyme which occurs
because of the gene mutations of the GALT enzyme, hence leading to the accumulation of metabolites of galactose metabolism that are galactitol and galactose-1phosphate [10]. Galactose-1-phosphate can accumulate in all tissues and inhibit
other enzymes too as phosphoglucomutase and glucose-6-phosphate dehydrogenase
[14]. Newborn infants with classic galactosemia show normal weight at birth but
their weight shows a decline as they start feeding [15]. Newborns with this disorder
are asymptomatic but as they are exposed to milk, life-threatening symptoms start
appearing which include difficulties in feeding, renal tubular dysfunction, hypoglycemia, hepatomegaly, vomiting, diarrhea, and cataracts. Speech difficulties, cognitive disabilities, visual perceptions, hypergonadotropic hypogonadism, and reduced
bone mass are the long-term complications [8]. The mortality rate of classic galactosemia is 1 in 40,000 to 60,000 newborns [15]. Immediate restriction of galactose
containing foods is a primary treatment of classic galactosemia. Instead of this, soy
milk, amino acids-based formulas, or formulas with other carbohydrate sources are
preferred [10].
Fig. 2.2 Schematic representation of the Leloir pathway of galactose metabolism. ATP adenosine
triphosphate, ADP adenosine diphosphate, UDP uridine diphosphate, PPi inorganic pyrophosphate, GALK galactokinase
H. Sharif et al.