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A structural difference between the cell surfaces of humans and the great apes
E A Muchmore1, S Diaz, A Varki
1UCSD Cancer Center, Division of Hematology-Oncology, University of California San Diego, La Jolla 92093-0687, USA.
American Journal of Physical Anthropology
|October 24, 1998
Summary
Humans lack N-glycolyl-neuraminic acid (Neu5Gc) on most cells, unlike great apes and other mammals. This difference stems from a suppressed enzyme activity after human-ape divergence, potentially impacting cell interactions and host-pathogen recognition.
Area of Science:
- Biochemistry
- Evolutionary Biology
- Cell Biology
Background:
- Sialic acids, like N-acetyl-neuraminic acid (Neu5Ac), are crucial cell surface components in deuterostomes.
- Previous research indicated humans might lack N-glycolyl-neuraminic acid (Neu5Gc), a hydroxylated sialic acid variant.
Purpose of the Study:
- To investigate the presence and distribution of Neu5Gc in humans compared to other primates and mammals.
- To explore the biosynthetic pathway and evolutionary implications of Neu5Gc expression differences.
Main Methods:
- Comparative analysis of Neu5Gc presence in human and great ape plasma proteins, erythrocytes, lymphoblastoid cells, and various tissues.
- Investigation of the enzymatic activity responsible for Neu5Gc synthesis in human and chimpanzee cells.
Main Results:
- Neu5Gc is abundant in great apes and other mammals but virtually absent in human plasma and erythrocytes.
- Enzymatic activity for Neu5Gc production is present in chimpanzees but absent in humans.
- Traces of Neu5Gc are found in some human tissues, cancers, and fetal tissues, suggesting suppressed but not entirely absent capacity.
Conclusions:
- Humans lost the enzymatic capacity to synthesize Neu5Gc after divergence from the hominid lineage.
- This widespread structural difference in cell surface sialic acids may have functional consequences for cell-cell interactions and host-pathogen recognition in humans.
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