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Structures for the ABO(H) Blood Group: Which Textbook Is Correct? John M. Risley Department of Chemistry, The University of North Carolina at Charlotte, Charlotte, NC 28223-0001;
[email protected] When teaching about carbohydrates from biochemistry textbooks and some organic chemistry textbooks, one invariably encounters the ABO(H) blood group. With the importance and interest generated from the considerable research on the ABO(H) blood group, one assumes that college textbooks should contain the correct structures for each of the A, B, and O(H) antigens. However, after students in a firstsemester biochemistry class were asked to draw the structures for the ABO(H) blood group for a discussion of carbohy-
Figure 1. The correct molecular structures for each of the O(H), A, and B antigens of the ABO(H) blood group are shown with the shorthand notation. Each antigen is attached through the Galβ(1→ ) linkage to the nonreducing end of various heterosaccharide cores of glycoproteins and glycolipids that are not a part of the specific blood group. Abbreviations: Fuc, L-fucose; Gal, galactose; GalNAc, Nacetylgalactosamine.
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drates, one student raised the question, “Why are the structures of the ABO(H) blood group different in my biochemistry textbook (1) from those in my organic chemistry textbook (2)?” Six biochemistry textbooks (1, 3–7), an organic chemistry textbook (2), and two Internet sites1 (8, 9) were compared. Structures for the ABO(H) blood group were found in six of these textbooks (1–6) and at the two Internet sites (8, 9). Schwartz (10) in Devlin’s textbook (7) provided a general description of the antigens’ syntheses, but did not give structural formulas. There was no agreement among the various molecular structures for the A, B, and O(H) antigens from the different sources. While there are some superficial similarities among them, each of the structures is different! Which, if any, of these structures is correct for the ABO(H) blood group? Schenkel-Brunner’s monograph (11), a FactsBook (12), and the primary literature were expected to provide the correct antigen structures. A search of “structures of ABO blood group” on SciFinder Scholar (in Dec 2005) returned 146 references where the two concepts “structures” and “ABO blood group” were closely associated with one another. Also, 1014 references were returned where the two concepts “structure” and “ABO blood group” were present anywhere in the reference. Two primary literature articles were chosen (13, 14). Based on Schenkel-Brunner’s monograph (11) and on the two articles in the biochemical literature (13, 14), none of the structures in the textbooks or at the Internet sites are correct. An additional reference (12) contains structures similar to those in the textbooks and at the Internet sites. The O(H) antigen is a disaccharide, L Fucα(1→2)Galβ(1→ ), on which the A and B antigens are synthesized by specific glycosyltransferases to give GalNAcα(1→3)[L-Fucα(1→2)]Galβ(1→ ) for the A antigen and Galα(1→3)[L-Fucα(1→2)]Galβ(1→ ) for the B antigen.2 Figure 1 shows the correct structures for the O(H), A, and B antigens. These specific O(H), A, and B antigens are attached at the nonreducing end of a heterosaccharide core. The structures of the heterosaccharide cores are dependent on the specific glycoprotein and glycolipid (11). Thus, the O(H), A, and B antigens in the six textbooks and at the two Internet sites are shown attached to various heterosaccharide cores. However, the entire structure (antigen plus heterosaccharide core) is then incorrectly identified as the O(H), A, or B antigen. The additional sugars that make up the heterosaccharide core should not be identified as parts of the antigens. In summary, when the ABO(H) blood group is used to illustrate the importance of carbohydrates in textbooks and in the classroom, it is very important to identify the specific molecular structures for the O(H), A, and B antigens. The confusing and erroneous impression must not be left that the various heterosaccharide cores are parts of the O(H), A, or B
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antigens, the complex sugars that elicit an antigenic response. Whenever the antigenic structures are shown attached to heterosaccharide cores of various glycoproteins and glycolipids, they must be clearly identified as such. Acknowledgments I wish to thank my student John D. Towle who asked the question that led to this investigation. I also wish to thank one reviewer for helpful comments. Notes 1. An MSN Search of “Structures of ABO Blood Group” returned 12,957 hits (in Dec 2005). 2. During the preparation of this article, an excellent discussion of the glycosyltransferases responsible for determining ABO(H) blood type was published in this Journal (15).
Literature Cited 1. Mathews, C. K.; van Holde, K. E.; Ahern, K. G. Biochemistry, 3rd ed.; Addison Wesley Longman: San Francisco, 2000; pp 309–310. 2. Solomons, T. W. G.; Fryhle, C. B. Organic Chemistry, 8th ed.; John Wiley & Sons: Hoboken, NJ, 2004; pp 1116–1117. 3. Berg, J. M.; Tymoczko, J. L.; Stryer, L. Biochemistry, 5th ed.; W. H. Freeman and Co.: New York, 2002; p 305. 4. Campbell, M. K.; Farrell, S. O. Biochemistry, 5th ed.; Thomson
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Brooks兾Cole: Belmont, CA, 2006; pp 458–459. 5. Voet, D.; Voet, J. G.; Pratt, C. W. Fundamentals of Biochemistry: Life at the Molecular Level, 2nd ed.; John Wiley & Sons: Hoboken, NJ, 2006; p 230. 6. Zubay, G. Biochemistry, 3rd ed.; Wm. C. Brown Publishers: Dubuque, IA, 1993; p 601. 7. Textbook of Biochemistry with Clinical Correlations, 6th ed.; Devlin, T. M., Ed.; John Wiley & Sons: Hoboken, NJ, 2006. 8. The ABO Blood Group System. http://www.life.rmit.edu.au/ mls/subjects/abo/resources/Structure1.htm (accessed Dec 2005). 9. Owen Foundation. http://www.owenfoundation.com/ Health_Science/ABO_Blood_Cells.html (accessed Jun 2007). 10. Schwartz, N. B. Carbohydrate Metabolism II: Special Pathways and Glycoconjugates. In Textbook of Biochemistry with Clinical Correlations, 6th ed.; Devlin, T. M., Ed.; John Wiley & Sons: Hoboken, NJ, 2006; pp 648–649. 11. Schenkel-Brunner, H. Human Blood Groups: Chemical and Biochemical Basis of Antigen Specificity, 2nd ed.; Springer: Wien, Austria, 2000; pp 54–183. 12. Reid, M. E.; Lomas-Francis, C. The Blood Group Antigen FactsBook; Academic Press: San Diego, 1997; pp 19–26. 13. Patenaude, S. I.; Seto, N. O. L.; Borisova, S. N.; Szpacenko, A.; Marcus, S. L.; Palcic, M. M.; Evans, S. V. Nature Struc. Biol. 2002, 9, 685–690. 14. Lee, H. J.; Barry, C. H.; Borisova, S. N.; Seto, N. O. L.; Zheng, R. B.; Blancher, A.; Evans, S. V.; Palcic, M. M. J. Biol. Chem. 2005, 280, 525–529. 15. Rose, N. L.; Palcic, M. M.; Evans, S. V. J. Chem. Educ. 2005, 82, 1846–1852.
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