ENZYMES PRESENT IN EUKARYOTIC CELL

ENZYMES PRESENT IN EUKARYOTIC CELL : 

ENZYMES PRESENT IN EUKARYOTIC CELL Wajiha jamal Student of MS Biochemcistry

Topics covered in this presentaion : 

Topics covered in this presentaion Enzymes Eukaryotic cell Synthesis of enzymes Targeting of enzymes Location of enzymes in cell significance of knowing the exact location of enzymes

What are enzymes : 

What are enzymes Enzymes are biological catalyst which speeds up the reaction time with out being consumed With few exceptions all most all enzymes are globular protein. In this regard enzymes can also be defined as A protein that accelerates a biochemical reaction. Thus they are polymers of amino acids linked together in a linear fashion forming long polypeptide chains. The sequence of amino acid in a enzyme is specific being, determined by the structure of genetic material of the cell.

Eukaryotic Cells : 

All eukaryotic cell have a membrane bound nucleus and a number of other membrane bound sub-cellular (internal) organelles, each of which has a specific function These membrane bound organelles include Nucleus Mitochondria Lysosme Endoplasmic Reticulum Cytosol peroxisome Eukaryotic Cells

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Thus the study of eukaryotic cells is essentially the exploration of these intracellular membrane- bounded compartments that house various cellular activities. Whether we consider the storage and transcription of genetic information, the biosynthesis of secretary proteins, the breakdown of long chain fatty acids or any of the many process occurring within the eukaryotic cells, several if not all of these reactions of pathway occur within a distinct membrane- bounded organelle.

How are the organelles able to perform their respective biological function ? : 

How are the organelles able to perform their respective biological function ? In order for an organelle to perform its assign specific vital function all the membrane bound intracellular organelles are gifted by the enzymes required for these biological reactions.

Enzyme biosynthesis in the cell : 

Enzyme biosynthesis in the cell As enzyme are protein in nature their biosynthesis is same as protein synthesis, also known as translation which can be defined as The transcription of a specific DNA base sequence into mRNA and its translation, by a ribosome, into a particular amino acid sequence forming a protein. The site of transcription is nucleus Where as the location for protein synthesis or translation is cytoplasm

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So in order for translation to occur the mRNA must exit the nucleus, and enter the cytoplasm. In cytoplasm the site of protein synthesis are RIBOSMES Post Translational Modification Release of a completed polypeptide chain from a ribosome is often not the last chemical step in the formation of a protein. During or after synthesis, the polypeptide progressively assumes its native conformation with the formation of appropriate hydrogen bonds and vander waals, ionic and hydrophobic interactions. In this way the linear or one dimensional genetic message of mRNA is converted into the three dimensional structure of the protein

Post Translational Modification : 

Post Translational Modification Protein folding Trimming Covalent Modification Hydroxylation Phosphorylation Glycosylation addition of carboxyl group attachment of lipids N-acylation

Why post-translational processing? : 

Why post-translational processing? adds functionality effects targeting regulates activity increases mechanical strength changes recognition

Protein Targeting : 

Protein Targeting Cells must ensure that each synthesized proteins is sorted to its correct location where it can carry out the appropriate function. This process is called protein targeting. In a eukaryotic cell the protein may be destined to stay in the cytosol, it may need to be targeted to an organelle (mitochondria, nucleus, chloroplast etc) or be inserted into the plasma membrane or exported out of the cell

Signals for protein targeting : 

Signals for protein targeting The signals involved are also called sorting signals.  They are regions on the targeted protein with certain amino acid sequences. These signals interact with specific receptors, either on the target organelle or a carrier protein.

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There are two basic forms of targeting pathways: post-translational targeting: nucleus mitochondria chloroplasts peroxisomes co-translational targeting: ER Golgi lysosomes plasma membrane secreted proteins

Location of enzymes in eukaryotic cell : 

Location of enzymes in eukaryotic cell

Enzymes present in nucleus : 

The enzymes of the nucleus can be grouped according to their location within the nucleus In the soluble space. Bound to chromatin Concentrated in the nucleolus Bound to membrane Enzymes present in nucleus

Enzyme present in mitochondria : 

Enzyme present in mitochondria

Enzymes present in mitochondria : 

Enzymes present in mitochondria Mitochondria are organelles consisting of different parts. It consist of various enzymes involved in different metabolism like carbohydrate, fatty acids and nitrogen metabolism . Besides enzymes of electron transport and oxidative phosphorylation are also located in mitochondria These principal enzymes found in this organelle are localized in different regions like The mitochondria matrix Inner membrane of mitochondria Intermembrane space Outer membrane of matrix

Enzyme present in Endoplasmic Reticulum : 

Enzyme present in Endoplasmic Reticulum

Enzymes Present In Endoplasmic Reticulum : 

Enzymes Present In Endoplasmic Reticulum A large number of different processes occur on the endoplasmic reticulum including protein synthesis, protein folding, and protein transport, biosynthesis of fatty acids, sterols, phospholipids, and the metabolism of foreign compounds, and this is reflected in the enzyme composition. There are two forms of endoplasmic reticulum Smooth endoplasmic reticulum Rough endoplasmic reticulum

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Enzymes of Smooth endoplasmic reticulum Cholesterol biosynthetic enzymes Steroid hydroxylation enzymes drug-metabolizing enzymes (aromatic ring hydroxylation, side-chain oxidation deamination, dealkylation, dehalogenation) Enzymes of Rough endoplasmic reticulum Protein synthesis Glucose 6-phosphatase

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The ER consists of two sides namely The cytosolic side The luminal side 1. Enzymes of Cytosolic side Protein synthesis Adenosinetriphostase Cytochrome b5 reductase NADPH-cytochrome reductase GDPmannose α-D-mannosyltransferase 5' Nucleotidase Cholesterol acyltransferase

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2. Enzymes of luminal side Glucose 6-phosphatase Nucloesidediphosphatase β-D-Glucuronidase Protein disulphide isomerase Proline cis-trans isomerase

Enzymes present in lysosome: : 

Enzymes present in lysosome: Proteolytic enzymes   Cathepsins B. D, G, L Elatase Collagenase   Enzymes for Hydrolysis of glycosides   β-D-Glucuronidase β -W-Acetyl-n-hexosaminidase Hyaluronoglucoasminidase Lysozyme Neuraminidase

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Nucleic acid Hydrolyzing enzymes   Deoxyribonucleic II Ribonuclease II Lipid Hydrolyzing enzmyes Phospholipases A1 and A2 Cholesterol esterase

Enzymes Present In Peroxisome : 

Enzymes Present In Peroxisome Peroxisomes contain a range of enzymes involved in oxidative reactions. They are bounded by a single membrane In some plant tissues they are also found to contain enzymes of the glyoxalate cycle and are called glyoxysomes. They contain a range of flavin oxidases that generate hydrogen peroxide. They also contain catalase Mammalian peroxisomes have also been implicated in cholesterol biosynthesis .They are abundant in tissues that are active in lipid metabolism

Enzymes Present In Cytosol : 

Enzymes Present In Cytosol A large number of enzymes are present in the cytosol, particularly those responsible for glycolysis, gluconeogenesis, fatty-acid synthesis, nucleotide biosynthesis, and aminoacyl-RNA synthesis. listed (A) Carbohydrate metabolism Glycolytic enzymes including phosphorylase, phosphorylase kinase, and protien kinase Glycogen synthase Fructose-bisphosphatase

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(B) Enzymes of the pentose phosphate pathway Malate dehydrogenase Isocitrate dehydrogenase Lactate dehydrogenase Malate dehydrogenase (c) Lipid metabolism Acetyl CoA carboxylase Fatty-acid synthase complex Glycerol-3-phosphate dehydrogenase (NAD+) (D) Amino-acid and protein metabolism Aspartate aminotransferase Arginase Argininosuccinate lyase Aminoacyl-tRNA synthetases (E) Nucleic-acid synthesis Nucleoside kinase Nucleotide kinase

Not all enzymes are confined to a specific organelle : 

Not all enzymes are confined to a specific organelle In some cases the enzyme is present at only one location within the cell while in other the enzymes for certain biochemical reactions may be present in different organelle. For example : The enzyme content of the soluble compartment of the nucleus is similar to that of the cytosol, especially in regard to that of the enzymes of the glycolytic pathway. All enzymes found on the nuclear mebrane except cytochrome c oxidase are also found in the ER

Importance of enzymes location in organelles : 

Importance of enzymes location in organelles The knowledge of correct location of enzymes is of great importance as the enzymes are not only used by the body to perform the vital functions but infect are very significant in different studies for the benefit of living organisms. These studies could either use enzymes to study the different uncountable metabolic processes Besides it is also useful in isolating the different organelle as they can be used to check the purity of the fractionated organelle by measuring the activity of a particular enzyme which is the characteristic of that organelle and is not found any where else in the cell such enzymes are also Marker enzymes.

Marker Enzymes : 

Marker Enzymes

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Thank you