Bioinorganic Chemistry FKIP

7/30/2019 Bioinorganic Chemistry FKIP

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Bioinorganic Chemistry

Ilham Maulana

Chemistry Dept. FMIPA Unsyiah



Scope of Bioinorganic Chemistry….

a field that examines the role of metals in biology

includes the study of both natural phenomena such as

the behavior of metalloproteins as well as artificially

introduced metals, including those that are non-

essential, in medicine and toxicology also includes the study of inorganic models or mimics

that imitate the behaviour of metalloproteins




Major Areas of Bioinorganic Chemistry….

Metal ion transport andstorage


Proteins and small molecules whose

aim is to carefully control the

concentration of metal ions in the cell

(sometimes referred to as metallome)




Metal ion transport andstorage Hydrolase enzymes


a diverse collection of proteins that

interact with water and substrates.

Examples of this class of

metalloproteins are carbonicanhyydrase, metallophosphatases,

and metalloproteinases.




Metal ion transport andstorage Hydrolase enzymes Metal-containing electron

transfer proteins


These electron transport proteins are

complementary to the non-metal

electron transporters nicotinamide

adenine dinucleotide (NAD) and flavin

adenine dinucleotide (FAD).





transfer proteins

Oxygen transport andactivation proteins


extensive use of metals such as iron,

copper, and manganese in

transporting oxygen (Hemoglobin,

Myoglobin). Some metalloproteins are

designed to protect a biological system

from the potentially harmful effects of

oxygen and other reactive oxygen-containing molecules such as

hydrogen peroxide





transfer proteins


Bioorganometallic systems


more focused on the utilization of

metals by unicellular organisms





transfer proteins


Bioorganometallic systems The nitrogen metabolism

pathways


Metals that facilitate the metabolism of

Nitrogen. Nitrogenase is one of themore famous metalloproteins

associated with nitrogen metabolism





transfer proteins


Bioorganometallic systems The nitrogen metabolism

pathways Metals in medicine


the study of the design and

mechanism of action of metal-

containing pharmaceuticals, and

compounds that interact with

endogenous metal ions in enzyme

active sites. This diverse field includes

the platinum and ruthenium anti-cancer drugs, chelating agents, gold

drug chaperones, and gadolinium

contrast agents.



Metals and Toxicity….

The vast majority of biochemical processes in which a

metal plays a role involve a only a relatively small

number of metals. Those metals include Na, K, Mg,

Ca, Mo, or the fi rst-row transition metals from V to Zn.

(Only molybdenum could be considered as a heavy

metal)

Generally, heavy metals having low charge ( “ soft ” )are toxic (Hg, Pb, Cd, Tl, etc).

Some heavy metals bind to groups such as the

sulfhydryl (-SH) group in enzymes, destroying the

ability of the enzyme to promote the reaction in anormal way

Beryllium is an extremely toxic metal that is not soft




Metals and Toxicity….

one way that toxicity of metals rises is by substitutionfor another metal (Cd for Zn, Be for Mg…)

When this happens, the enzyme loses its activity

numerous nonmetallic substances that are toxic

(cyanides, carbon monoxide). The toxicity of these

materials is related to their being potential ligands that

attach to metals in specific structures,which thereby

prevents the metals from serving their normal

functions.




Metals and The Action….

One way in which metals function in biochemicalstructures is in enzyme activity

The function of enzymes as catalysts: Absolute specifi city, Group specifi city, Linkage specifi city,Stereochemical specifi city

Enzymes may not function well or at all unless some

other species known as a cofactor is present The most interesting cofactors are metal ions Mg 2+,

Ca2+, K+ , Fe2+ , or Cu2+

The combination of enzyme and cofactor is known asthe holoenzyme





One of the most important metals with regard to its rolein enzyme chemistry is zinc (carboxypeptidase A and

B, alkaline phosphatase, alcohol dehydrogenase,

aldolase, and carbonic anhydrase)

Carbonic anhydrase, which contains a single zinc atom

in its structure, has a molecular weight of about 30,000.

In this structure, zinc is surrounded tetrahedrally by

three histidine molecules and one water molecule.

h3ZnOH2 + H2O → H3O+ + h3ZnOH-

h3ZnOH- + CO2 → HCO3- + h3Zn






Ribbon diagram showing human carbonic

anhydrase II. The grey sphere is the zinc

cofactor in the active site.



Photosynthesis….

6 CO2 + 6 H2O → C6H12O6 + 6 O2

the reaction requires energy from light, so, it is known

as photosynthesis

The structures that are responsible for absorption of light in order for its energy to be used are the

chlorophylls, which contain porphyrin-type ligands.

The porphyrin structure is derived from the basic unit

known as porphin The chlorophylls consist of several members of a

series, which have structures derived from a molecule

known as chlorin




Photosynthesis….

porphin chlorophyll




Oxygen Transfer….

the transport of oxygen by heme is the basis for respiration

Heme is one of several proteins that contain iron

When an oxygen molecule is attached to the iron and it

changes from high spin to low spin, the size of the

Fe2+ changes. The ionic radius of Fe 2+ in the high

spin state is approximately 78 pm, but in a low-spin

environment it is about 61 pm.

This reduction in size is suffi cient to allow the Fe2+

ion to fit between the nitrogen atoms in the porphyrinring.




Oxygen Transfer….

By the usual standards of coordinate bond strength,

the binding of oxygen to

iron in hemoglobin is quite

weak.

On the other hand, groupssuch as CN-, CO, H 2S,

and others bind strongly to

Fe2+ . Thus these

substances are highly toxic,and they function by

preventing the uptake of

oxygen.


Bioinorganic Chemistry FKIP

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