= Carissa L. White
{c}
Carissa L. White coauthored a 2002 study identifying a <heparosan synthase>. The characterized <glycosyltransferase> combined two sugar-transfer activities in one <protein>, building a <heparosan> chain from <glucuronic acid> and <N-acetylglucosamine> units. The product was the unsulfated, unepimerized backbone related to <heparin>, rather than a fully modified <heparin> molecule.<Identification and molecular cloning of a heparosan synthase from Pasteurella multocida type D by P. L. DeAngelis and Carissa L. White>[Abstract, Journal of Biological Chemistry 277 (2002), pp. 7209–7213; DOI 10.1074/jbc.M112130200.]{ref}
The study tested which <nucleotide sugars> supported chain formation and compared the product's susceptibility to different <polysaccharide>-cleaving <enzymes>. An illuminating distinction is between building a repeating backbone and modifying that backbone: identifying a <heparosan synthase> establishes a particular polymerization activity, but does not establish all the later reactions needed to make a differently substituted <glycosaminoglycan>. The reported one-<protein>, two-activity mechanism also shows that two alternating chemical additions need not require two separate <polypeptides>.<Identification and molecular cloning of a heparosan synthase from Pasteurella multocida type D by P. L. DeAngelis and Carissa L. White>[Abstract: dual-action transferase, donor specificity and product digestion.]{ref}
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