Tujuan mempelajari metabolisme mikroorganisme Memahami jalur biosintesis suatu metabolit (primer atau sekunder) yang diproduksi olehmikroorganisme Memahami regulasi dalam proses metabolisme (inhibisi, represi, kontrol, induksi) Memanfaatkan mikroorganisme untuk memproduksi metabolit yang kita inginkan Dapat memanipulasi mikroorganisme dan lingkungannya untuk mengatur laju pembentukan metabolit yang kita inginkan Dapat menetapkan faktor-faktor penentu dalam suatu proses metabolisme •
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Aktivitas metabolisme mikroba •
Aktivitas metabolisme utama yang dilakukan di lakukan mikroorganisme
1. Metabolisme karbohidrat : amilum dan selulosa diubah menjadi glukosa dan selanjutnya menjadi senyawa lain mis.asam organik, aldehid atau alkohol. Dengan adanya oksigen senyawa tersebut diubah menjadi CO2 dan H2O 2. Metobolisme lemak : lemak diubah menjadi gliserol dan asam-asam lemak (proses lipolisis) li polisis) 3. Metobolisme protein dan asam amino : protein diuraikan di uraikan menjadi asam amino dan selanjutnya di dekarboksilasi
KATABOLISME •
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Katabolisme : proses degradasi nutrien menjadi fragmenfragmen yang lebih kecil. Proses katabolisme menghasilkanATP, proton motive force, menurunkan tenaga dan pengambilan nutrisi serta pembentukan rangka karbon dalam jalur metabolisme inti Jalur degradasi ini bisa pendek (misalnyapembentukan asetat) atau bisa pula panjang (misalnya pembentukan pembentukan asam benzoat)
Amphibolisme : proses pembentukan intermediate (senyawa antara) Terjadi pembentukan building blocks (senyawa pembangun), misalnya misalnya asam amino, purin, pirimidin, gula-gula fosfat, asam organik, dan metabolit lain
Anabolisme : biosintesis polimer dari monomer (asam amino, nukleotida dan lipid) dari rangka karbon utama melalui pemanfaatan ATP dan NADPH.
Pertumbuhan Pertumbuhan sel dengan menggabungkan struktur makromolekul melalui proses polimerisasi monomer-monomer yang dihasilkan dari proses biosintesis,melibatkan berbagai nukleotida fosfat Polimer sel Misal: protein, asam nukleat, dinding sel, makanan cadangan.
METABOLISM REGULATION
Bacteria have developed phisticated mechanisms for the regulation of both catabolic and anabolic pathways. Generally, bacteria do not synthesize degradative (catabolic) enzymes unless the substrates for these enzymes are present in their environment. For example, synthesis of enzymes that degrade lactose would be wasteful unless the substrate for these enzymes (lactose) is available in the environment. Similarly, bacteria have developed diverse mechanisms for the control of biosynthetic (anabolic) pathways. pathways.
Bacterial cells shut down biosynthetic pathways when the end product of the pathway is not needed or is readily obtained by uptake from the environment. For example, if a bacterium ba cterium could find a preformed amino acid like tryptophan in its environment, it would make sense to shut down its own pathway of tryptophan biosynthesis, and thereby thereby conserve energy energy. However, However, in real bacterial life, the control mechanisms for all these metabolic pathways pathways must be reversible, since the environment can change quickly and drastically.
Fungsi enzim dalam metabolisme Reaksi metabolisme dikatalisis oleh enzim Semua protein pada sel tunggal (unisel) berada dalam bentuk protein enzim Pada Pada bakteri, kebanyakan tidak memiliki protein struktur Setiap enzim secara spesifik bertanggung jawab pada konversi suatu senyawa menjadi senyawa lain Kerja enzim dapat bersifat substratspesifik, atau kerja-spesifik
Regulasi metabolisme Seluruh kegiatan metabolisme berlangsung sangat cepat dan harus bekerja di dalam sel Mikroorganisme Mikroorganisme memiliki potensi genetik untuk memproduksi lebih dari 1000 enzim Enzim ini harus dibentuk dalam jumlah yang tepat dan dalam da lam sistem yang terkoordinasi terkoordinasi dengan baik agar a gar sel bekerja secara efisien Mikroorganisme Mikroorganisme dapat dengan cepat mengantisipasi perubahan lingkungan sehingga dapat dengan segera memperbaiki sistem metabolismenya Regulasi untuk sistem yang demikian terjadi pada level sintesis enzim atau pada level kerja enzim
Faktor yang mempengaruhi regulasi metabolisme Jenis dan jumlah enzim Jenis dan jumlah substrat Adanya induktor, aktivator, represor dan inhibitor Faktor lingkungan Faktor genetik
Pada Pada tingkat apa regulasi itu terjadi? ter jadi? Tingkat molekul : misalnya regulasi terhad terhadap ap ATP ATP,, NADPH Tingkat efektor : misalnya cAMP, Guanosin Trifosfat Tingkat protein : ekspresi oleh gen tertentu, induksi enzim
Perbedaan Inhibitor, Represor, Aktivator dan Induktor terhadap suatu enzim Inhibitor : molekul atau senyawa yang yang dapat menginhibisi atau menghambat terjadinya suatu reaksi Represor :molekul atau senyawa yang menyebabkan berkurangnya berkurangnya kecepatan reaksi enzim Induktor : molekul atau senyawa yang dapat menyebabkan terjadinya terjadinya peningkatan efek enzim yang lebih baik Aktivator : molekul atau senyawa yang dapat mengaktifkan kerja suatu enzim
Regulasi enzim terdapat dalam 2 bentuk yaitu 1. Regula Regulasi si nonk nonkov ovale alen n yait yaitu u terik terikatn atny ya efekto efektorr oleh oleh produk pada daerah alosterik secara non kovalen 2. Regula Regulasi si modifi modifikas kasii kov kovalen alen yait yaitu u mene menempe mpelny lnyaa gugus kimia mis: fosfat atau nukleotida pada enzim
Regulasi non kovalen 1. Inhibisi umpan balik Reaksi umpan balik yaitu penghabatan reaksi reaksi biosintesis biosintesis oleh produk akhir yang berperan sebagai alosterik negatif pada percabangan enzim (corepressor enzim) Jika enzim dihambat oleh satu produk produk akhir saja, maka disebut inhibisi umpan balik sederhana Jika dihambat oleh 2 produk akhir akhir,, disebut inhibisi umpan balik kumulatif Jika dihambat oleh 2 produk akhir akhir secara terus menerus sampai terhambat disebut inhibisi umpan balik terkonsnetrasi
Conditions Affecting Enzyme Formation in Bacteria
bacterial cells can change change patterns of enzymes, in order to adapt them to their specific environment. Often the concentration of an enzyme in a bacterial cell depends on the presence of the substrate for the enzyme. Constitutive enzymes are always produced by cells independently of the composition of the medium in which the cells are grown. T Ex: the enzym for operate during glycolysis and the TCA cycle are generally constitutive: they are present at more or less the same concentration in cells at all times. Inducible enzymes are produced ("turned on") in cells in response to a particular substrate; they are produced only when needed. In the process of induction, the substrate, or a compound structurally similar to the substrate, formation of the enzyme and is called an inducer.
A repressible enzyme is one whose synthesis is downregulated or "turned off" by the presence of (for example) the end product of a pathway pathway that the enzyme normally participates in. the end product is called a corepressor of the enzyme.
Regulation of Enzyme Reactions Not all enzymatic reactions occur in a cell to the same extent. Some substances are needed in large amounts and the reactions involved involved in their synthesis must therefore occur in large amounts. Other substances are needed in small amounts and the corresponding reactions involved involved in their synthesis need only occur in small amounts.
In bacterial cells, enzymatic reactions may be regulated by two unrelated modes: (1) control control or regulation regulation of enzyme enzyme activity activity (feedback inhib inhibition ition or end product inhibition), which mainly operates to regulate biosynthetic pathways pathways (2) control or regulation of enzyme synthesis, 2a. end-product repression, which functions in the regulation of biosynthetic pathways pathways 2b. enzyme induction and catabolite repression, which regulate
The process of feedback inhibition regulates the activity of preexisting enzymes in the cells. The processes of end-product repression, enzyme induction and catabolite repression are involved in the control of synthesis of enzymes. The processes which regulate the synthesis of enzymes may be either a form of positive positive control or negative negative control. End-product repression and enzyme induction are mechanisms of negative negative control because they lead to a decrease in the rate of transcription t ranscription of proteins. Catabolite repression is considered a form of positive control because it affects an increase increase in rates of transcription transcription of proteins.
ALLOSTERIC PROTEIN
An allosteric protein is one which has an active (catalytic) site and an allosteric (effector) site. In an allosteric enzyme, the active site binds to the substrate of the enzyme and converts it to a product. The allosteric site is occupied by some small molecule which is not a substrate. When the allosteric site is occupied by the effector molecule, the configuration of the active site is changed so that it is now unable to recognize and bind to its substrate .
The protein is an enzyme, when the allosteric site is occupied, the enzyme is inactive, i.e., the effector molecule decreases the activity of the enzyme (fig 1) There is an alternative situation The effector molecule of certain allosteric enzymes binds to its allosteric site and and consequently transforms the enzyme from an inactive to an active state Some multicomponent allosteric enzymes have several sites occupied by various effector molecules that modulate enzyme activity over a range of conditions.
Fig. 1. An allosteric enzyme with a negative effector site. When the effector molecule binds to the allosteric site, substrate binding and catalytic activity of the enzyme are inactivated. When the effector is detached from the allosteric site the enzyme is active
Example of an allosteric enzyme with a positive effector site. The effector molecule binds to the allosteric site resulting in alteration of the active site that stimulates substrate binding and catalytic activity.
Some allosteric proteins are not enzymes , but nonetheless have an active site and an allosteric site. The regulatory proteins that control metabolic pathways pathways involving end product repression, enzyme induction and catabolite repression are allosteric proteins. In their case, the active site is a DNA binding site , which, when active, binds to a specific sequence of DNA, and which, when inactive, does not bind to DNA. The allosteric or effector molecule is a small molecule which can occupy the allosteric site and affect aff ect the active site. enzyme repression, a positive effector molecule (called a corepressor) binds to the allosteric regulatory protein and activates its ability to bind to DNA. enzyme induction a negative effector molecule (called an inducer) binds to the allosteric site, causing the active site to change conformation thereby detaching the protein from its DNA binding site.
