The enzyme carboxypeptidase A catalyzes the hydrolysis of the peptide ARELC in 1

Question

The enzyme carboxypeptidase A catalyzes the hydrolysis of the peptide ARELC in 10 mM phosphate buffer at pH 7.0. The enzyme is known to obey Michaelis-Menten kinetics. Under the conditions of this experiment: V_max = 10 mmol/min/mg and Km (ARELC) = 0.20 mM Draw the structure of the peptide represented by the one-letter amino acid abbreviations ARELC at pH 7.0. What is the net charge of ARELC at pH 2.0? Suppose that the substrate concentration of ARELC in this assay is 500 uM. Calculate the expected initial velocity. Suppose another substrate was tested under the same conditions at pH 7.0, AGELC, and it was determined that the Km of AGELC was 5 mM. Which substrate has the HIGHER affinity for carboxypeptidase A? Explain your reasoning. Draw a typical plot of V vs. [S] for this enzyme that follows Michaelis-Menten kinetics. Label the axes and use the units defined for V_max and Km at the beginning of the question. Draw a new graph showing how this plot changes when converted to a Lineweaver-Burk Double Reciporocal plot. Be sure to label the axis. Use the units as defined in the questions. In the graph drawn in part (f) indicate what the x-intercept represents and what the y-intercept represents. AGELC acts as a competitive inhibitor of the enzyme. In the LWB plot you drew in part (f), draw and label a second line depicting how the inhibitor would cause the enzyme to act. Be sure to clearly label both lines.

Explanation / Answer

Answer:

a) The peptide consists of amino acid ARELC is

Alanine-Arginine-Glutamic acid- Leucine-Cystein

b) Because aminoacids contain both acidic (-NH3+) group and basic -COO-) group, they are amphoteric.

In an acidic solution pH=2.0 , -COO- group is protonated to a free -CooH group and the molecule has an over all positive charge

c)

The M-M reaction is ploted as

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