BAHAN KULIAH BIOKIMIA POWER POINT BAGIAN 1 /BIOCHEMISTRY POWER POINT LECTURES PART 1 | Karya Tulis Ilmiah

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Protein Function

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Quaternary structure of deoxy- and oxyhemoglobin

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D-2,3-bisphosphoglycerate (BPG)

BPD binds to hemoglobin and decreases the oxygen affinity and keeps it in the deoxy form.

BPG binds 1:1 with a K=1x10-5 M to the

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BPG binds specifically to the deoxy state and

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At 100 torr or arterial blood, hemoglobin is 95% saturated

At 30 torr or venous blood, hemoglobin is 55% saturated

Hemoglobin releases 40% of its oxygen. In the

absence of BPG, little oxygen is released. Between BPG, CO₂, H+, and Cl- all O

2 binding is accounted

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BPG restores the 37% release of O₂ at higher

elevations

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Hemoglobin mutants

There are about 500 variants of hemoglobin 95% are single amino acid substitution.

5 % of the worlds population carries a different sequence form the normal.

•Changes in surface charge

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Changes in surface rarely change the function of hemoglobin with the exception of the sickle cell mutation.

Internal residues cause the hemoglobin to contort to different shapes and alter its binding properties. Heinz bodies are

precipitated aggregates of hemoglobin. Usually cause hemolytic anemia characteristic by cell lysis.

Hb Hammersmith Phe CD1(42)  Ser. The Phe wedges the heme in place, without it the heme falls out of the protein.

Hb Bristol Val E11(67)  Asp occludes O₂ from the pocket.

Hb Bibba substitutes a Pro in the middle of H helix kinks the chain.

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Stabilizing Methemoglobin. Or the Fe(III) state eliminates the oxygen binding to the heme. Diagnostic of a blue color or cyanosis.

Hb Boston His E7(58)  Tyr (the distal His)

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Hb Iwate His F8(87)  Tyr “black mouth disease Japan

They have chocolate brown blood.

Changes at the 1-2 interface usually have lower Hill

coefficients. Stabilize either the T or R state

Polycythemia, a ruddy complexion

Hb Yakima Asp G1(99)  His eliminates H-bonding that stabilizes the T form at the 1-2 interface and

stabilizes the R state P₅₀ =12 torr

Hb Kansas Asn G4(102)  Thr eliminates H-bonding

that stabilizes the T form at the 1-2 interface and so

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Fetal Hemoglobin

•Fetal hemoglobin has a different  subunit called a 

subunit or ₂_2.

•In Fetal hemoglobin, BPG does not affect this variant and the baby’s blood will get its oxygen from the

mothers hemoglobin.

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