Question

Lactose operon produces which of the following enzymes?

• A. $\beta$-galactosidase, permease and glycogen synthase
• B. $\beta$-galactosidase, permease and transacetylase
• C. Permease, glycogen synthase and transacetylase
• D. $\beta$-galactosidase, permease and phosphoglucose isomerase

Answer 1

Answer: (B)

$\beta$-galactosidase, permease and transacetylase

Phosphoglucose isomerase catalyzes the conversion of glucose-6-phosphate into fructose 6-phosphate which is the second step of glycolysis. Glycogen synthase catalyzes elongation of glycogen chains. The lac operon is an operon responsible for transport and metabolism of lactose in Escherichia coli and other bacteria and carries the genes that codes for enzymes involved in lactose metabolism only. This makes options A, C and D wrong. The lac operon has three structural genes. The lac Z gene codes for $\beta$-galactosidase which converts lactose into glucose and galactose. The lac Y gene that codes for $\beta$-galactoside permease which transports lactose into the cell. The lac A gene codes for $\beta$-galactoside transacetylase. Option B is the correct answer.