Cathepsin D and 2',3'-cyclic nucleotide 3'-phosphohydrolase in developing human foetal brain

Novel 29 kDa heparin-binding lectin from human foetal brain

Heparin inhibitable lectins are physiologically important because of their interactions with extracellular matrix and with other cell surface glycoconjugates. However, due to the unstable nature of these animal lectins, it becomes necessary to purify them in the shortest possible time. In the present study, a chromatographic procedure was developed to separate heparin inhibitable lectin activity. Lectin activities from human foetal brain were separated on a Q-Sepharose column employing different equilibration conditions. When proteins were loaded on to a phosphate-buffered saline (PBS) equilibrated column and eluted with salt gradient, only one lectin peak was obtained. However, when proteins were loaded on to a hypotonic equilibrated column and eluted with a salt gradient, four lectin peaks were obtained. The lectin peak obtained from the PBS equilibrated column was characterized as heparin inhibitable lectin. On SDS-PAGE analysis, it gave a single band of 29 kDa. For optimum lectin activity, a pH of around 7.0 was required. Lectin activity was stimulated by Mn++; amino acid composition was different from other known lectins. The lectin was particularly rich in acidic amino acids. Regional distribution of 29 kDa lectin in different foetal brain regions gave the highest content in the cerebral cortex, showing a caudoroastral distribution. Determination of the subcellular distribution of the lectin in the foetal cerebral cortex gave the highest value with a mitochondrial fraction.