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Chapter 6: Problem 21

Dlinical Application of Differential Enzyme Inhibition Human blood serum contains a class of enzymes known as acid phosphatases, which hydrolyze biological phosphate esters under slightly acidic conditions \((\mathrm{pH} .0)\) : Acid phosphatases are produced by erythrocytes and by the liver, kidney, spleen, and prostate gland. The enzyme of the prostate gland is clinically important, because its increased activity in the blood can be an indication of prostate cancer. The phosphatase from the prostate gland is strongly inhibited by tartrate ion, but acid phosphatases from other tissues are not. How can this information be used to develop a specific procedure for measuring the activity of prostatic acid phosphatase in human blood serum?

Short Answer

Expert verified
Add tartrate to inhibit prostatic enzyme and compare with untreated sample.

Step by step solution

01

Understand the Enzyme Background

Acid phosphatases are enzymes that hydrolyze phosphate esters under acidic conditions and are present in various tissues including the prostate gland. Prostatic acid phosphatase is an important marker for prostate cancer because its activity increases in the blood when the cancer is present.
02

Identify the Inhibitor

Tartrate ion is identified as a specific inhibitor for the prostatic acid phosphatase enzyme. This means that when tartrate is present, it inhibits the activity of prostatic acid phosphatase, but not the acid phosphatases from other tissues.
03

Analyze the Inhibition Significance

Because tartrate inhibits only the prostatic acid phosphatase, this inhibitor can be used to distinguish the enzyme activity from other acid phosphatases in blood serum. This selective inhibition is crucial for developing a specific measurement.
04

Develop a Specific Procedure

To measure the activity of prostatic acid phosphatase, blood serum can be divided into two samples. Tartrate is added to one sample to inhibit the prostatic acid phosphatase. Both samples are then tested for acid phosphatase activity. By comparing the two, the difference in activity can be attributed to the prostatic acid phosphatase alone.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Acid Phosphatases
Acid phosphatases are a group of enzymes found in many tissues throughout the body. They perform the important task of hydrolyzing phosphate esters, which means they help break down compounds that contain phosphate groups. This process typically occurs under slightly acidic conditions, usually around a pH of 5.0 to 6.0.

These enzymes are produced by various organs including the liver, kidney, spleen, erythrocytes (red blood cells), and notably, the prostate gland. Each type of acid phosphatase may vary slightly depending on where it is produced, serving essential roles in different biological processes. Their ability to function under acidic conditions makes them unique, as many biochemical reactions in the body occur closer to neutral pH values.
Prostatic Acid Phosphatase
Prostatic acid phosphatase (PAP) is a specific form of acid phosphatase that is produced predominantly by the prostate gland. This enzyme has proven particularly useful in medical diagnostics, especially for conditions related to the prostate. Its main function, similar to other acid phosphatases, is to hydrolyze phosphate esters.

PAP becomes highly relevant in the context of prostate cancer. When prostate cancer develops, the amount of this enzyme in the blood serum typically increases. Therefore, measuring PAP levels can serve as an important marker for detecting and monitoring prostate cancer. Elevated PAP levels often suggest possible recurrence or progression of the disease, and as such, this enzyme is a crucial part of prostate cancer diagnostics.
Tartrate Inhibition
Tartrate inhibition refers to the process of using tartrate ions to specifically inhibit the activity of certain enzymes, particularly those linked with the prostate gland. Tartrate ions have the unique ability to selectively inhibit prostatic acid phosphatase without affecting other types of acid phosphatases found in different tissues.

This specific inhibition proves invaluable in medical diagnostics, as it allows lab technicians to differentiate between prostatic acid phosphatase activity and other acid phosphatases in blood serum. By using tartrate, it becomes possible to isolate and measure the activity of prostatic acid phosphatase specifically, aiding in the accurate detection and monitoring of prostate cancer.
  • Selective inhibition allows for focused analysis of PAP.
  • Enables differentiation from other similar enzymes.
Prostate Cancer Biomarkers
Prostate cancer biomarkers are substances that can be measured in the body and may point to the presence or progression of prostate cancer. Prostatic acid phosphatase is one such traditional biomarker for this disease. Its levels in the blood increase significantly when prostate cancer is present, making it a useful marker for diagnosis and management.

In a clinical setting, these biomarkers help doctors to not only diagnose but also track how prostate cancer responds to treatment. They are critical in understanding whether the cancer is advancing, receding, or remaining stable.
  • Primary role: Early detection and ongoing monitoring of prostate cancer.
  • Can indicate progression or recurrence of cancer.
Understanding and employing biomarkers effectively enables physicians to provide better-targeted treatments and improve patient outcomes.

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Most popular questions from this chapter

Protection of an Enzyme against Denaturation by Heat When enzyme solutions are heated, there is a progressive loss of catalytic activity over time due to denaturation of the enzyme. A solution of the enzyme hexokinase incubated at \(45{ }^{\circ} \mathrm{C}\) lost \(50 \%\) of its activity in \(12 \mathrm{~min}\), but when incubated at \(45^{\circ} \mathrm{C}\) in the presence of a very large concentration of one of its substrates, it lost only \(3 \%\) of its activity in \(12 \mathrm{~min}\). Suggest why thermal denaturation of hexokinase was retarded in the presence of one of its substrates.

Kinetic Inhibition Patterns Indicate how the observed \(K_{\mathrm{m}}\) of an enzyme would change in the presence of inhibitors having the given effect on \(a\) and \(\alpha^{\prime}\) : a. \(\alpha>\alpha^{\prime} ; \alpha^{\prime}=1.0\) b. \(\alpha^{\prime}>\alpha\) c. \(\alpha=\alpha^{\prime} ; \alpha^{\prime}>1.0\) d. \(\alpha=\alpha^{\prime} ; \alpha^{\prime}=1.0\)

Estimation of \(V_{\max }\) and \(\boldsymbol{K}_{\mathrm{m}}\) by Inspection Graphical methods are available for accurate determination of the \(V_{\max }\) and \(K_{\mathrm{m}}\) of an enzyme-catalyzed reaction. However, these quantities can sometimes be estimated by inspecting values of \(V_{0}\) at increasing [S]. Estimate the \(V_{\max }\) and \(K_{m}\) of the enzyme-catalyzed reaction for which the data in the table were obtained. \begin{tabular}{cc} {\([\mathbf{S}](\mathrm{M})\)} & \(V_{0}(\mu \mathrm{M} / \mathrm{min})\) \\ \hline \(2.5 \times 10^{-6}\) & 28 \\ \(4.0 \times 10^{-6}\) & 40 \end{tabular} \begin{tabular}{ll} \(1 \times 10^{-5}\) & 70 \\ \(2 \times 10^{-5}\) & 95 \\ \(4 \times 10^{-5}\) & 112 \\ \(1 \times 10^{-4}\) & 128 \\ \(2 \times 10^{-3}\) & 140 \\ \(1 \times 10^{-2}\) & 139 \\ \hline \end{tabular}

Irreversible Inhibition of an Enzyme Many enzymes are inhibited irreversibly by heavy metal ions such as \(\mathrm{Hg}^{2+}, \mathrm{Cu}^{2+}\), or \(\mathrm{Ag}^{+}\), which can react with essential sulfhydryl groups to form mercaptides: $$ \text { Enz-SH }+\mathrm{Ag}^{+} \rightarrow \text { Enz-S-Ag }+\mathrm{H}^{+} $$ The affinity of \(\mathrm{Ag}^{+}\)for sulfhydryl groups is so great that \(\mathrm{Ag}^{+}\) can be used to titrate - SH groups quantitatively. An investigator added just enough \(\mathrm{AgNO}_{3}\) to completely inactivate a \(10.0 \mathrm{~mL}\) solution containing \(1.0 \mathrm{mg} / \mathrm{mL}\) enzyme. A total of \(0.342 \mu \mathrm{mol}\) of \(\mathrm{AgNO}_{3}\) was required. Calculate the minimum molecular weight of the enzyme. Why does the value obtained in this way give only the minimum molecular weight?

Applying the Michaelis-Menten Equation IV Researchers discover an enzyme that catalyzes the reaction \(\mathrm{X} \rightleftharpoons \mathrm{Y}\). They find that the \(K_{\mathrm{m}}\) for the substrate \(\mathrm{X}\) is \(4 \mu \mathrm{M}\), and the \(k_{\text {cat }}\) is \(20 \mathrm{~min}^{-1}\). a. In an experiment, \([\mathrm{X}]=6 \mathrm{mM}\), and \(V_{0}=480 \mathrm{nM} \mathrm{min}^{-1}\). What was the \(\left[\mathrm{E}_{\mathrm{t}}\right]\) used in the experiment? b. In another experiment, \(\left[\mathrm{E}_{\mathrm{t}}\right]=0.5 \mu \mathrm{M}\), and the measured \(V_{0}=5 \mu \mathrm{M} \mathrm{min}^{-1}\). What was the \([\mathrm{X}]\) used in the experiment? c. The researchers discover that compound \(Z\) is a very strong competitive inhibitor of the enzyme. In an experiment with the same \(\left[E_{t}\right]\) as in (a), but a different \([\mathrm{X}]\), they add an amount of \(\mathrm{Z}\) that produces an \(a\) of 10 and reduces \(V_{0}\) to \(240 \mathrm{nM} \mathrm{min}^{-1}\). What is the \([\mathrm{X}]\) in this experiment? d. Based on the kinetic parameters given, has this enzyme evolved to achieve catalytic perfection? Explain your answer briefly, using the kinetic parameter(s) that define catalytic perfection.
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