Name: graphing enzyme kinetics data
Uploaded: 2023-04-30T10:09:42.000Z
Duration: 1 min 19 s
Channel: JoVE

K12 Standards

north-carolina-k-12-science-standard-course-of-study

North Carolina K-12 Science Standard Course of Study

9-12

Biology

from-molecules-to-organisms-structures-and-processes

From Molecules to Organisms- Structures and Processes

LS.Bio.1.2

Introduction to Enzyme Kinetics

קינטיקה של אנזימים חוקרת את שיעורי התגובות המזורזות על ידי אנזימים. שיעורי הניסויים החוזרים ונשנים בריכוזי מצע משתנים מנוטרים על ידי מדידת ריכוז המצע הנצרך או המוצר שנוצר לאורך זמן.
תוצאות אלה יכולות להיות גרפיות כדי להראות כיצד ריכוז המצע משפיע על קצב או מהירות התגובה.
מהירות התגובה עולה באופן ליניארי עם הגדלת כמויות המצע בריכוזים נמוכים, אך היא מתחילה להתייצב בריכוזים גבוהים יותר. הקצב מתקרב למהירות מקסימלית או Vmax – הקצב שבו האנזים רווי לחלוטין בסובסטרט.
זיקה לאנזים מודדת באיזו עוצמה או חולשה אנזים קושר את הסובסטרט שלו ומכומת על ידי KM, קבוע מיכאליס. הערך של KM שווה לריכוז המצע כאשר השיעור הוא 50% מה- Vmax.
KM קטן מצביע על כך שלאנזים יש זיקה גבוהה לסובסטרט ולהפך. אנזים עם KM גדול יותר דורש ריכוזי סובסטרט גבוהים יותר כדי להתקרב למהירות המקסימלית שלו בהשוואה לאנזים עם KM נמוך יותר.

<ol>
	<li>Voet D. and Voet J.G. Biochemistry, מהדורה רביעית, John Wiley & Sons, 2010, pp-487-492</li>;
	<li>Berg J.M., Tymoczko J.L., and Stryer L. Biochemistry, 5th ed, W.H. Freeman and Co., Section 8.4</li>
</ol>

מבוא לקינטיקה אנזימטית

<div style="direction: rtl;">
קינטיקה אנזימטית חוקרת את קצבי התגובות הביוכימיות. מדענים עוקבים אחר קצבי התגובה עבור תגובה אנזימטית מסוימת בריכוזי מצע שונים. ניתן לבצע גם ניסויים נוספים עם מעכבים או מולקולות אחרות המשפיעות על קצב התגובה.

הנסיין יכול אז לשרטט את קצב התגובה הראשוני או את המהירות (Vo) של הניסוי הנתון כנגד ריכוז המצע ([S]) כדי לקבל גרף של תכונות התגובה. עבור תגובות אנזימטיות רבות המערבות מצע בודד, נתונים אלה מתאימים למשוואת מיכאליס-מנטן, שנגזרה על ידי לאונור מיכאליס ומוד מנטן.

<img alt="Eq1" src="/files/ftp_upload/12164/12164_Equation 1.png" style="text-align: center; height: 70px;" />

המשוואה מעריכה את המהירות המקסימלית (Vmax) ואת קבוע מיכאליס (KM) עבור האנזים הנחקר ומבוססת על ההנחות הבאות:

<ol>
	<li>אין תוצר נוכח בתחילת התגובה.</li>
	<li>קצב היווצרות קומפלקס אנזים-מצע שווה לקצב הניתוק והפירוק לתוצרים.</li>
	<li>ריכוז האנזים הוא מינימלי בהשוואה לריכוז המצע.</li>
	<li>רק קצבי התגובה הראשוניים נמדדים.</li>
	<li>האנזים נמצא או בצורתו החופשית או בקומפלקס האנזים-מצע.</li>
</ol>

סידורים מחדש שונים של משוואת מיכאליס-מנטן, כגון גרף לינוויבר-בורק, גרף אדי-הופסטי וגרף האנס-וולף, הם דרכים חלופיות לייצג גרפית את הפרמטרים הקינטיים. לעתים קרובות נעשה שימוש בגרף לינוויבר-בורק או גרפים הדדיים כפולים להערכת ה-KM וה-Vmax. הגרף משתמש בערכי ההדדיות של ציר ה-x וה-y מהגרף של מיכאליס-מנטן. מבחינה מתמטית, נקודת החיתוך עם ציר ה-y שווה ל-1/Vmax, ונקודת החיתוך עם ציר ה-x שווה ל-−1/KM.

ניתן להשתמש בגרף לינוויבר-בורק כדי להבדיל חזותית בין סוגי מעכבים - תחרותיים, לא תחרותיים ובלתי תחרותיים. סידורים מחדש שונים של משוואת מיכאליס-מנטן, כמו גרפי אדי-הופסטי וגרפי האנס-וולף, גם הם משמשים לקביעת פרמטרים קינטיים.
</div>

קינטיקה של אנזימים חוקרת את שיעורי התגובות הביוכימיות. מדענים עוקבים אחר קצבי התגובה לתגובה אנזימטית מסוימת במצעים שונים ...

Education

JoVE Core

Cell Biology

ביולוגיה של התא

Unit 1

יחידה 1

Energy and Catalysis

אנרגיה וקטליזה

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

graphing enzyme kinetics data

Enzyme kinetics uses graphs to show how fast a biochemical reaction happens. Scientists measure the initial reaction rate, or velocity (Vo), at different substrate concentrations ([S]). They may also run trials with inhibitors or other molecules that change the reaction rate.

The results are often plotted as Vo against [S]. For many single-substrate reactions, the data fits the Michaelis-Menten equation. This equation, named after Leonor Michaelis and Maud Menten, helps estimate the maximum velocity (Vmax) and the Michaelis constant (KM) for the enzyme being studied.

The Michaelis-Menten model is based on a few assumptions. No product is present at the start of the reaction. The rate of enzyme-substrate complex formation equals the rate of its breakdown into products and its dissociation. The enzyme concentration is minimal compared with the substrate concentration. The model also uses only the initial reaction rates. In this setup, the enzyme is either free or bound in an enzyme-substrate complex.

Scientists can also use other graph forms to analyze the same data. The Lineweaver-Burke plot, also called the double reciprocal plot, uses the reciprocal values from the Michaelis-Menten graph. On this plot, the y-intercept equals 1/Vmax and the x-intercept equals -1/KM. It is often used to estimate KM and Vmax and to visually distinguish competitive, non-competitive, and uncompetitive inhibitors.

Other rearrangements of the Michaelis-Menten equation include the Eadie-Hofstee plot and the Hanes-Woolf plot. These graphs are also used to determine kinetic parameters. Together, these methods help scientists compare reaction behavior and understand how enzymes respond to substrate concentration and inhibitors.

Graphing Enzyme Kinetics Data

the first law of thermodynamics

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introduction to enzyme kinetics

Enzyme kinetics uses graphs to show how fast a biochemical reaction happens. Scientists measure the initial reaction rate, or velocity (Vo), at different substrate concentrations ([S]). They may also run trials with inhibitors or other molecules that change the reaction rate. The results are often plotted as Vo against [S]. For many single-substrate reactions, the data fits the Michaelis-Menten equation. This equation, named after Leonor Michaelis and Maud Menten, helps estimate the maximum...

turnover number and catalytic efficiency

How Fast Enzymes Work in Digestion

Enzymes can work at very different speeds, and their turnover number shows how fast they convert substrate molecules into products. Turnover number is the maximum number of substrate molecules an enzyme can transform per unit time. For most enzymes, this value is between 1 and 1000 molecules per second. Some enzymes are especially fast. Catalase has the highest known turnover number and can convert up to 2.8×10^6 molecules of hydrogen peroxide into water and oxygen each second. Lysozyme has...

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atp energy storage and release

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key terms and concepts

Learn how enzyme kinetics data is graphed with Michaelis-Menten, Lineweaver-Burke, Eadie-Hofstee, and Hanes-Woolf plots to estimate Vmax and KM.

Graphing Enzyme Kinetics Data | JoVE K12

cell biology

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Virginia  Standards of Learning

HIgh School

BIO.2

BIO.2.c

Chemistry

CH.7

CH.7.f

Florida Department of Education

High School

Life Science

SC.912.L.18

SC.912.L.18.4

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Graphing Enzyme Kinetics Data

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