Humic Acids and their Biospecific Interactions with Lectins

摘要

Humic matter occupies a unique position in the natural environment, bridging the biotic and abiotic kingdoms (1). Unlike biological macromolecules with a specific purpose (proteins, nucleic acids etc.) formation of humic compounds is not under genetic control. Much has happened in humic substances research in the past years to make evidence of structures and to identify molecular building blocks of humic acids (HA). There is not much work done to identify structures and binding of sugar building blocks in HA. Also the interactions of HA with sugar-binding proteins like lectins via their sugar moieties remain, however, to be elucidated. The present work deals with the analyses of sugar content and sugar composition of HA isolated from brown coal, peat and soils. In addition to HA of natural origin highly glycosylated HA were synthesized via non-enzymatic and chemical glycosylation. The carbohydrate content was quantified and carbohydrate residues identified qualitatively. In accordance with their glycan parts HA react reversibly with mannose or galactose recognizing plant lectins like concanavalin A (ConA) and mistletoe lectin I (ML I), respectively.