Biochemistry of ABO Antigens
Summary
TLDRThis video delves into the biochemical basis of the blood group system, explaining how different antigens form on the surface of red blood cells (RBCs). It clarifies that blood groups are determined by the presence of A, B, or both antigens, or the absence of any, resulting in the O blood group. The H antigen, present in all individuals, serves as a precursor for A and B antigens, with specific enzymes coded by the A and B alleles catalyzing their formation. The video also addresses the null alleles in O blood group individuals, which do not add to the H antigen, maintaining its original form.
Takeaways
- 🧬 The human blood group system is determined by the surface proteins, specifically antigens, present on red blood cells (RBCs).
- 🔍 There are four main blood groups: A, B, AB, and O, with the H antigen being a common precursor for A and B antigens.
- 🌐 The H antigen locus on chromosome 19 contains the fucosyltransferase gene, which is crucial for the formation of the H antigen.
- 🔬 Individuals with blood group O have null alleles, resulting in no additional molecules being added to the H antigen, leaving only the H antigen on RBCs.
- 📚 The H antigen is a basic structure consisting of a trisaccharide with fucose, galactose, and N-acetylglucosamine.
- 🧬 In individuals with blood group A, the A allele codes for an enzyme that adds a specific sugar to the H antigen, forming the A antigen.
- 🧬 For blood group B, the B allele produces an enzyme that modifies the H antigen to create the B antigen.
- 🔄 The process of blood group antigen formation involves specific enzymes transferring sugars to the H antigen precursor on the RBC surface.
- 🧬 The presence of A, B, or both A and B antigens on RBCs is determined by the expression of the respective alleles and the activity of their enzymes.
- 📝 The video script provides a biochemical explanation of how different blood group antigens are formed from a common precursor, the H antigen.
- 👍 The video encourages viewers to like and subscribe for more content on the topic.
Q & A
What is the primary determinant of an individual's blood group?
-An individual's blood group is determined by the surface proteins, specifically the antigens present on the surface of red blood cells (RBCs).
What are the four main blood groups found in the human population?
-The four main blood groups are A, B, AB, and O.
What is the significance of the H antigen in the context of blood groups?
-The H antigen is significant as it acts as a precursor molecule for both A and B antigens and is present on the surface of RBCs in all individuals, regardless of their blood group.
What is the role of the FUT1 gene in the formation of blood group antigens?
-The FUT1 gene codes for the α-1,2-fucosyltransferase enzyme, which is responsible for transferring fucose sugar from GDP-fucose to the oligosaccharide chain on the RBC surface, forming the H antigen.
How does the presence of the null allele affect the blood group of an individual?
-The presence of the null allele in individuals with blood group O results in the production of a non-functional protein, which does not add any molecules to the precursor H antigen, leaving the RBCs with only the H antigen.
What enzyme does the A allele code for, and what is its function in blood group formation?
-The A allele codes for an enzyme called GalNAc transferase or α1,3-N-acetylgalactosaminyltransferase, which catalyzes the transfer of N-acetylgalactosamine to form the A antigen from the H antigen.
What is the enzyme coded by the B allele, and how does it contribute to the formation of the B antigen?
-The B allele codes for the enzyme called galactose transferase, which transfers galactose to the H antigen, catalyzing the formation of the B antigen.
What is the basic structure of the oligosaccharide molecule found on immature RBCs before any antigen addition?
-The basic structure of the oligosaccharide molecule on immature RBCs consists of fucose, galactose, and N-acetylglucosamine.
How does the chromosome 19 contribute to the blood group system?
-Chromosome 19 contains the H locus, which includes the FUT1 gene responsible for the production of the α-1,2-fucosyltransferase enzyme, essential for the formation of the H antigen.
What is the biochemical process that leads to the formation of A and B antigens from the H antigen?
-The formation of A and B antigens from the H antigen involves the action of specific transferase enzymes coded by the A and B alleles, which catalyze the addition of N-acetylgalactosamine and galactose, respectively, to the H antigen.
Why do individuals with blood group AB have both A and B antigens on their RBCs?
-Individuals with blood group AB have both A and B antigens on their RBCs because they express both the A allele, which codes for the enzyme to form the A antigen, and the B allele, which codes for the enzyme to form the B antigen.
Outlines
🌟 Blood Group Biochemistry Introduction
This paragraph introduces the topic of the video, which is the biochemistry of the blood group system. It explains that an individual's blood group is determined by the surface proteins, or antigens, present on red blood cells (RBCs). The human population has four main blood groups: A, B, AB, and O. The script clarifies that the O blood group does not have any A or B antigens but does have the H antigen, which is a precursor for A and B antigens. The video promises to delve into the formation of these antigens from the H antigen through the action of specific enzymes.
🧬 The Structure and Formation of Blood Group Antigens
This paragraph delves into the biochemical processes that lead to the formation of different blood group antigens. It describes the immature RBCs, which have an oligosaccharide molecule on their surface, the basic structure of which is composed of fucose, galactose, and N-acetylglucosamine. The chromosome 19 contains the H locus, which includes the H gene responsible for the fucosyltransferase enzyme. This enzyme transfers fucose to the oligosaccharide chain, creating the H antigen. The paragraph then explains how different alleles (A and B) code for specific enzymes that modify the H antigen to form A and B antigens, respectively. The A allele produces an enzyme that adds an additional galactose, forming the A antigen, while the B allele produces an enzyme that modifies the fucose to form the B antigen.
🔬 Genetic Determinants of Blood Group Antigens
This paragraph discusses the genetic basis for the presence or absence of A and B antigens on RBCs. It explains that individuals with the O allele are homozygous for a null allele, which does not produce a functional protein to modify the H antigen, leaving it as the only antigen present. In contrast, individuals with the A or B alleles have functional enzymes that add specific sugars to the H antigen, resulting in the formation of A or B antigens. The paragraph also explains that individuals with both A and B alleles will have both A and B antigens on their RBCs due to the presence of both enzymes.
Mindmap
Keywords
💡Multiple Alleles
💡Blood Group System
💡Antigens
💡Red Blood Cells (RBCs)
💡H Antigen
💡Null Alleles
💡Precursors
💡Fucosyltransferase
💡Galactosyltransferase
💡Oligosaccharide Chain
💡Chromosome 19
Highlights
The video discusses the biochemistry of the blood group system, focusing on the formation of antigens on the surface of red blood cells (RBCs).
Blood groups are determined by the surface proteins present on RBCs, with four main types: A, B, AB, and O.
The H antigen is a precursor molecule for both A and B antigens and is present on the surface of all RBCs.
Individuals with blood group O have null alleles and do not produce any additional antigens beyond the H antigen.
The H antigen locus on chromosome 19 contains the H gene, which codes for a fucosyltransferase enzyme.
Fucosyltransferase transfers fucose sugar from GDP-fucose to the oligosaccharide chain on the RBC surface, forming the H antigen.
Blood group A individuals have the A allele, which codes for an enzyme that adds an N-acetyl-D-galactosamine to the H antigen to form the A antigen.
Blood group B individuals have the B allele, which codes for an enzyme that adds D-galactose to the H antigen to form the B antigen.
The A and B antigens are formed from the H antigen through the action of specific transferase enzymes.
The video explains the biochemical process behind the formation of A, B, and AB blood groups from the H antigen.
Individuals expressing both A and B alleles will have both A and B antigens present on their RBCs.
The video clarifies the misconception that O blood group individuals lack antigens, when in fact they have the H antigen.
The biochemical pathways for the formation of blood group antigens are detailed, emphasizing the role of specific enzymes.
The video provides a clear understanding of the genetic basis for the different blood groups found in the human population.
The importance of the H antigen as a fundamental component of the blood group system is highlighted.
The video concludes by summarizing the key points of the blood group system's biochemistry and encourages viewer engagement.
Transcripts
Oh in the previous video we discussed
about the multiple alleles by taking the
example of leads pond within the
population now in this video we'll be
discussing about the biochemistry of
blood group system while we will be
discussing about the formation of
different antigens on the surface of
ultra sites when we talk about the blood
group of an individual is determined by
the surface proteins on it resides it is
actually what kind of antigen is present
on the surface of RBC's in human
population the system has poor
possible blood groups found within the
population it's a blood group B blood
group a B blood group and Oh blood group
in case of a blood group individuals the
a antigen is present on the surface of
RBC's in case of B blood group
individuals the B antigen is present on
the surface of RBC's in case of a B
individuals both antigens are present on
the surface of RBC's and in all
individuals the H antigen is present on
the surface of RBC's do not get confused
here that may be sometimes you might
have heard that or individuals like any
antigen on RBC's it's because the or
individuals have null alleles and do not
go for any addition of molecules on the
precursor molecule which is already
present here in the form of H antigen
and this H antigen acts as a precursor
molecule for both a and B antigens which
we are going to discuss later on in this
video now looking at the structure of
immature RBC that's devoid of any
antigen yet it has got oligosaccharide
molecule on its surface having a
structure that consists of wilcos
galactose and Estelle glucose mine and
galactose this is the basic structure of
alpha site prior to any addition of
fully functional surface antigens after
that the chromosome number 19 has got H
locus that's the H antigen locus which
consists of fut one gene at antigen gene
and this fut one gene codes for pure
Cosell transferase enzyme we see the
function of mucosal transferase enzyme
is that it will transfer the Fuko sugar
from Gd
chuckles molecule towards the
oligosaccharide chain on
RBC surface as you can see in this
diagram on this addition the surface
molecule is now called H antigen and
this H antigen molecule is precursor for
both a and B antigens now we have four
scenarios here individuals expressing a
lead individual is expressing B allele
individual is expressing Oly Oly in
homo-sex condition or individuals
expressing both a and B allele
now let's take our individuals first the
individuals were or allele in homozygous
condition this allele is null allele and
it will produce a non-functional protein
and this non-functional protein will not
add any molecule to the precursor h
antigen for the h antigen on the surface
of RBC remains as such in its form in Oh
blood group individuals that's why we
say Oh blood group individuals does not
have surface antigen but actually they
have the H antigen on its surface that's
already present prior to orally
expressing now we have individuals
expressing a allele and individuals
expressing ble the a allele codes for an
enzyme called gal neg transferase or
simply an a style glucosamine
transferase whereas the B allele codes
for the enzyme called gal transferase
the RBC has precursor molecule in the
form of H antigen only to surface as
shown in the figure and to that gal Lake
transferase catalyzed the reaction of
transfer of cowl-neck or simply a nest
alkaloid Tosa my this catalyzes the
formation of a antigen from h antigen
then we have B allele expressing
individuals while we get gal transferase
enzyme and this gal transferase enzyme
transfers their like toes towards the
edge antigen which catalyzes the
formation of B antigen from H antigen so
this is how the formation of a and B
antigen takes place from H antigen with
the transferase enzymes so this is all
about biochemistry op blood group
system I hope you liked the video if you
liked it give it a thumbs
and make sure to subscribe channel
thanks
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