Many glycosidases, which work as useful reagents for the studies of structures and functions of free and conjugated oligosaccharides, have been found and thoroughly purified. These enzymes are classified into exo- and endoglycosidases by their glycon specificities. Their usefulness and limits as reagents are explained in detail in this review.
Endoglycosidases, which were originally found in the culture fluid of bacteria and in the extracts of plants, are now widely found in the mammals including humans. The physiological roles of these enzymes are discussed in relation to the oligosaccharides accumulated in the urine of patients with exoglycosidase deficiencies. Furthermore, PNGase is found to play important roles in the ER-associated degradation pathway of glycoproteins.
Recent studies of the glycosidases in Bifidobacteria have revealed that GNB/LNB pathway, which uniquely exist in this bacteria, works for the expression of Bifidus factor activity of human milk oligosaccharides, an important topic in the baby nutrition. This interesting field will be introduced in detail in one section of this article.

(Communicated by Kunihiko SUZUKI, M.J.A.)

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Loss of terminally differentiated cardiomyocytes due to heart disease is irreversible and current therapeutic regimes are limited. Cell therapy using stem cell-derived cardiomyocytes is an attractive option to repair injured hearts. The discovery of direct reprogramming of fibroblasts into induced pluripotent stem cells (iPSCs) and successful differentiation of iPSCs into cardiomyocytes provided a revolutionary paradigm in heart regenerative research. During the past decades, significant advances in stem cell culture, differentiation and purification protocols, as well as in cell transplantation methodologies, have been achieved. On the other hand, recent studies demonstrated that a somatic cell could be converted into an alternative differentiated cell type without first becoming a stem cell by overexpression of lineage-specific factors. We found that functional cardiomyocytes can be directly induced from fibroblasts by a combination of three cardiac transcription factors, Gata4, Mef2c and Tbx5, in vitro and in vivo. I will review the perspectives of heart regeneration using reprogramming technology.

(Communicated by Hiroo IMURA, M.J.A.)

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