Metabolism of Monosaccharides and Disaccharides

Flashcards covering key terms and concepts related to the metabolism of monosaccharides and disaccharides, particularly focusing on fructose metabolism and its associated disorders.

Umax

The maximum rate of an enzyme-catalyzed reaction.

Km

The concentration of substrate required for the enzyme to achieve half of its maximum velocity (Vmax).

Fructose

A monosaccharide that is an isomer of glucose and is found in many foods.

Galactose

Another monosaccharide that is an isomer of glucose, usually obtained from lactose.

Sucrose

A disaccharide composed of glucose and fructose.

Lactose

A disaccharide composed of glucose and galactose.

Phosphorylation of Fructose

The process of adding a phosphate group to fructose, primarily by the enzymes hexokinase and fructokinase.

Hexokinase

An enzyme that phosphorylates glucose, indicating high affinity for glucose and low Km.

Fructokinase

An enzyme that specifically phosphorylates fructose, indicating high affinity for fructose and low Km.

Cleavage of F1P or F1,6BP

The process where fructose 1-phosphate or fructose 1,6-bisphosphate is split to produce intermediates for further metabolism.

Aldolase

An enzyme that cleaves fructose 1-phosphate into dihydroxyacetone phosphate and glyceraldehyde.

Essential Fructosuria

A benign genetic condition where fructose accumulates in the blood due to a deficiency in fructokinase.

Hereditary Fructose Intolerance (HFI)

A genetic disorder caused by a deficiency of the aldolase enzyme, leading to the accumulation of fructose 1-phosphate.

Symptoms of HFI

Include abdominal pain, hypoglycemia, vomiting, failure to thrive, hepatomegaly, jaundice, and chronic liver disease.

Diagnosis of HFI

Can involve detecting fructose in urine, enzyme assays, or DNA-based testing for aldolase deficiency.

Management of HFI

Involves avoiding foods containing fructose to prevent symptoms.