3.The effect of the hormones glucagon and insulin on PAH activity were investiga

Question

3.The effect of the hormones glucagon and insulin on PAH activity were investigated. The results are shown in Figure 4. In addition, the amount of radioactively-labeled phosphate incorporated into PAH with glucagon treatment was found to be nearly seven-fold greater than in controls 1200 1000 a) Why is radioactively labeled phosphate being incorporated into PAH? 600 400 200 insulin glucagen pre wPhe Figure 4-X activity of PAH in the presence and absence of insulin, glucagon, and/or preincubation with Phe. b) What does this tell you about the effect of glucagon on the activity of PAH? c) What is a very likely scenario for PAH activation (think about what we learned about second messengers)? Draw a clear diagram showing a possible mechanism for the hormonal activation of PAH.

Explanation / Answer

a) Radioactively labeled phosphate is incorporated into PAH to label PAH and measure the activity of PAH when effect of insulin and glucagon were measured.

b) Phenylalanine hydroxylase (PAH) enzyme used to catalyze the hydroxylation step of phenylalanine and then generate tyrosine. Tyrosine is required for generation of different hormones.Glucagon increases the activity of PHA almos seven fold more compared to control.

c) The possible mechanism of hormone activation of PAH might be through binding of hormone to hormone receptor and then by generating a cascade of signalling pathway through activation of second messenger system.

d) Phenylalanine hydroxylase (PAH) is necessary and required for degradation of phenylalanine to tyrosine and this step is required for metabolic pathway responsible for degradation of excess phenylalanine. Deficiency of PAH enzyme activity results in the formation of autosomal recessive phenylketonuria. Thus hormonal activation of PAH is an important aspect to regulate PAH level in body.

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