ENZYME BIOCHEMISTRY ENZYME INHIBITORS MLT 435 MOHD IKRAM BIN JAMALUDDIN (2021476898) MUHAMMAD FIQHI BIN ISHAMMUDDIN (2021461534) NURUL HUSNA BINTI ISMAIL (2021868064) NUR KHAIRUNNISA ISLAM BINTI FAIZAL SAZALI (2021834378) NOR ASYIRIN BINTI ZAINUDDIN (2021482726) WARDATUL IZZAH BINTI MOHAMAD RAZILLAH (2021853472) GROUP MEMBERS NAME: GROUP 6
REVERSIBLE E N Z Y M E I N H I B I T O R S molecules that bind to enzymes and inhibit their activity temporarily or permanently interact with enzymes in a way to slow down an enzyme-catalyzed process or prohibit enzymes from functioning normally E N Z Y M E S Proteins that catalyze chemical reactions in the body, and they are essential for many biological processes, including: Metabolism Signaling pathways Immune system T Y P E S O F I N H I B I T O R S Competitive Inhibtors Non-Competitive Inhibtors Uncompetitive Inhibtors Enzyme inhibitors play important roles in many biological processes, as they can regulate the activity of enzymes and pathways in the body INTRODUCTION
TYPES OF ENZYME INHIBITIONS 1. REVERSIBLE INHIBITION R e v e r s i b l e i n h i b i t i o n i s a n i n h i b i t i o n o f a n e n z y m e a c t i v i t y i n w h i c h t h e i n h i b i t i n g m o l e c u l a r e n t i t y c a n a s s o c i a t e a n d d i s s o c i a t e f r o m t h e p r o t e i n ’ s b i n d i n g s i t e . I n t e r m s o f a s p e c i f i c s u b s t r a t e , r e v e r s i b l e i n h i b i t o r s a r e e i t h e r c o m p e t i t i v e , n o n - c o m p e t i t i v e , o r u n c o m p e t i t i v e . 2. IRREVERSIBLE INHIBITION R e v e r s i b l e e n z y m e i n h i b i t o r s a r e b y p r o d u c t s o f e n z y m a t i c p r o c e s s e s . T h e b a l a n c e a n d m o s t e f f i c i e n t u s e o f m e t a b o l i c p a t h w a y s a r e s i g n i f i c a n t l y i n f l u e n c e d b y a n e n z y m e ' s r a t e d e c l i n e b r o u g h t o n b y t h e b u i l d u p o f i t s o w n p r o d u c t . I t s t o p s a n e n z y m e f r o m p r o d u c i n g m o r e n e w p r o d u c t s t h a n t h e f o l l o w i n g e n z y m e i n t h e c h a i n c a n h a n d l e . e . g i n h i b i t i o n o f h e x o k i n a s e b y a c c u m u l a t i n g g l u c o s e 6 - p h o s p h a t e D u e t o t h e n o n - c o v a l e n t i n t e r a c t i o n a n d r e v e r s i b l e e q u i l i b r i u m w i t h t h e e n z y m e , t h e e n z y m e a c t i v i t y i s r e s t o r e d w i t h a d e c r e a s e i n t h e i n h i b i t o r c o n c e n t r a t i o n . T h e d i s s o c i a t i o n e q u i l i b r i u m c o n s t a n t f o r e n z y m e i n h i b i t o r c o m p l e x e s i s k n o w n a s K i , w h i c h i s e q u a l t o [ E ] [ I ] / [ E I ] . L i n e w e a v e r - B u r k p l o t s s h o w t h e n o r m a l K m a n d / o r V m a x i n a w a y d e p e n d i n g o n t h e t y p e o f i n h i b i t o r , w h i c h r e f l e c t s t h e i n h i b i t i n g e f f e c t o f K i o n t h e r e a c t i o n k i n e t i c s ( N e l s o n , 2 0 0 8 ) .
Competitive enzyme inhibitor is one of the reversible inhibitors. A competitive inhibitor and the substrate cannot bind to the enzyme at the same time. This kind of inhibitor often has a very similar structure with the real substrate of the enzyme. The inhibition can be overcome with substrate concentration. (2) One way that an inhibitor can function is by blocking the active site. This is called competitive inhibition because the competitive inhibitor competes with the substrate for the active site. If the inhibitor beats the substrate to the active site, the substrate can’t get in and the reaction can’t happen. (3y) Competitive inhibitors are the inhibitors which only bind with enzymes, not enzyme-substrate complexes, because the affinity of substrate and enzyme have no major difference. The inhibitor has only affinity for the active side, not allosteric site. Once enzyme substrate complex is successfully produced then inhibitors cannot produce its effect. This type of inhibition can be overcome by adding high concentration of substrate. Degree of inhibition depends on the concentration of substrate and inhibitor. (1) The inhibitors bind the catalytic/substrate binding site. It competes with substrates for binding. Inhibition is reversible by increasing substrate concentration. Vmax constant, the substrate concentration has to be increased as reflected on increased Km. Therapeutic application Inhibitor does not change the shape of the active site of enzyme. If substrate concentration is increased, then inhibition rate is decreased. 1. COMPETITIVE INHIBITORS REVERSIBLE ENZYME INHIBITION F i g u r e f r o m h t t p s : / / i b . b i o n i n j a . c o m . a u / h i g h e r - l e v e l / t o p i c - 8 - m e t a b o l i s m - c e l l / u n t i t l e d - 6 / e n z y m e - i n h i b i t i o n . h t m l
2. UNCOMPETITIVE INHIBITORS Uncompetitive enzyme inhibitor is one of the reversible enzyme inhibitors. Uncompetitive inhibitors only bind to the complex of the enzymesubstrate and do not bind to the free enzymes. No structural similarities exist between the uncompetitive inhibitor and the substrate. They work by structural distortion of the active site. Binding site for inhibitor is created only when the substrate is bound to the active site. Although it binds outside of the active site, it can cause a complex enzyme's structural distortion at the active and allosteric sites and turns the catalysis inactive. After the change in active site, the structure of the biological agonist molecule could not bind with the active site. Pharmacological action is not produced if the agonist molecule does not appropriately bind to the active site. Figure from https://www.chem.purdue.edu/courses/chm333/Spring%202013/Lectures/Spring%202013%20Lecture%2016-%2017.pdf This kind of inhibition cannot be reversed by increasing substrate concentration until a saturating level but if it happens, it needs specialist treatment, such as dialysis. Additionally, multi-substrate enzymes exhibit this kind of inhibition, when the inhibitor competes with one substrate that it structurally resembles but is uncompetitive with the other. Uncompetitive reversible inhibition is uncommon, but it may happen in multimeric enzymes. One of the examples for uncompetitive enzyme inhibition is the inhibition of the key regulatory heme synthetic enzyme. REVERSIBLE ENZYME INHIBITION
The type of allosteric regulation An inhibitor that binds to an allosteric site, decreasing the enzyme's effectiveness Simply said, an allosteric site is one that differs from the active site, which is where the substrate binds. The inhibitor shares the same affinity for both the enzyme and the enzyme-substrate complex in noncompetitive inhibition because it binds at the allosteric site independently of substrate binding. When an inhibitor binds to the allosteric site, the active site have change their confirmation . Due to this modification, the active site and substrate no longer share specificity, making it impossible for the substrate to bind. Non competitive Inhibitors that are slow down an enzymecatalyzed process. The concentration of the substrate alone cannot overcome a non-competitive inhibitor. Non-competitive inhibition is significant because of how it controls metabolism through feedback inhibition. In feedback inhibition, the enzymes in a given metabolic pathway's products function as their own inhibitors. For illustrate, pyruvate kinase, the enzyme that catalyses the last stage of the glycolytic pathway, is inhibited by both alanine and ATP in a non-competitive mechanism. When sufficient amounts of the end product (ATP and alanine) are present, the inhibition of pyruvate kinase enables cells to stop breaking down glucose, preventing overproduction and energy waste IMPORTANCE OF NONCOMPETITIVE ENZYME INHIBITOR figure above was taken from that website:https://ib.bioninja.com.au/higher-level/topic-8- metabolism-cell/untitled-6/enzyme-inhibition.html 3. NON-COMPETITIVE INHIBITORS enzyme substrate inhibitor allosteric site active site REVERSIBLE ENZYME INHIBITION
Enzyme substrate forms enzyme substrate complex but the inhibitor can either bind to the enzyme substrate complex or it might bind to the enzyme competing with the substrate as well. Inhibitor may bind to the enzyme whether or not the enzyme has already bound the substrate but has a greater affinity for one state or the other. As a net result, product formation does not take place. Is called “mixed” as it can be seen as a mixture of competitive inhibition and uncompetitive inhibition in the way of the inhibitor operates. In competitive inhibition, the inhibitor can only bind the enzyme if the substrate has not already bound. In uncompetitive inhibition, the inhibitor can only bind the enzyme if the substrate has already bound. In mixed inhibition, the inhibitor binds to an allosteric site, the site different from the active site where the substrate binds. Nevertheless, not all inhibitors that bind to allosteric site are mixed inhibitors. Figure from http://guweb2.gonzaga.edu/faculty/cronk/CHEM245pub/kineticsinhibition.html 4. MIXED INHIBITORS REVERSIBLE ENZYME INHIBITION
IRREVERSIBLE INHIBITION A n e n z y m e i s i r r e v e r s i b l y i n h i b i t e d w h e n i t f o r m s a c o v a l e n t c o n n e c t i o n w i t h a s p e c i f i c g r o u p a t t h e a c t i v e s i t e . I n o t h e r w o r d s , a n i r r e v e r s i b l e i n h i b i t o r i s o n e t h a t w i l l r e s u l t i n a p e r m a n e n t l o s s o f e n z y m a t i c a c t i v i t y . T h e y a l s o a c t a s p o i s o n a n d d u e t o t h e s t r e n g t h o f t h e i n h i b i t o r - e n z y m e b o n d , n o a d d i t i o n o f e x c e s s s u b s t r a t e i s a b l e t o r e v e r s e t h e i n h i b i t i o n . A d d i t i o n a l l y , t h e y d e s t r o y a c r i t i c a l f u n c t i o n a l g r o u p o f t h e e n z y m e ' s a c t i v e s i t e o r b i n d s t a b l e n o n - c o v a l e n t l y w i t h i t . K i n e t i c a l l y , i r r e v e r s i b l e i n h i b i t o r s l o w e r t h e c o n c e n t r a t i o n o f a c t i v e e n z y m e , w h i c h l o w e r s t h e m a x i m u m c o n c e n t r a t i o n o f t h e E S c o m p l e x a n d , u l t i m a t e l y , l o w e r s t h e r a t e o f r e a c t i o n o f t h e i n d i v i d u a l e n z y m e m o l e c u l e s t h a t h a v e b e e n r e n d e r e d i n a c t i v e . W h e n t a k i n g i n t o a c c o u n t t h e i r K m a n d t u r n o v e r n u m b e r , t h e r e m a i n i n g u n c h a n g e d e n z y m e m o l e c u l e s a r e n o r m a l l y f u n c t i o n i n g . e . g N a t u r a l p o i s o n s a c t a s E n z y m e i n h i b i t o r s a n d I n h i b i t o r y e n z y m e s . I n n a t u r e , p o i s o n s a r e a b u n d a n t i n a n i m a l s a n d p l a n t s i n t h e f o r m o f p e p t i d e s a n d p r o t e i n s t h a t c a n i n h i b i t t h e a c t i v i t y o f e n z y m e s . S m a l l o r g a n i c c o m p o u n d s c a l l e d n a t u r a l t o x i n s s e r v e a s n a t u r a l i n h i b i t o r s o f n o n - c a t a l y t i c p r o t e i n s a n d e n z y m e s i n m e t a b o l i c p a t h w a y s . F i g u r e f r o m h t t p s : / / t h e b i o l o g y n o t e s . c o m / e n z y m e - i n h i b i t o r s /
The use of enzyme inhibitors can also have side effects, as they may affect the activity of other enzymes and pathways in the body. Therefore, it is important to carefully consider the potential risks and benefits of using enzyme inhibitors in therapeutic and research settings. Enzyme inhibitors have many potential applications, including: They are also used in research to study enzyme function and to identify potential drug targets. Overall, enzyme inhibitors are a powerful and versatile tool for understanding and modulating enzyme function, and they continue to be an active area of research and development in the fields of biology and medicine. Use as drugs to treat a variety of diseases such as cancer hypertension, and infections. Important to carefully consider the potential risks and benefits of using enzyme inhibitors in therapeutic and research settings. CONCLUSION
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