Brush border lactase-phlorizin hydrolase carries two catalytic sites. In the human enzyme lactase comprises Glu-1749, phlorizin hydrolase Glu-1273. The proteolytic processing of pro-lactase-phlorizin hydrolase by (rat) enterocytes stops two amino acid residues short of the N-terminus of`mature' final, brush border lactase-phlorizin hydrolase. Only these two amino acid residues are removed by luminal pancreatic protease(s), probably trypsin.z 1998 Federation of European Biochemical Societies.

The effect of glucose and fructose and fetal bovine serum on the expression of the fructose transporter GLUT5 was studied in clone PD7 of the human colon cancer cell line Caco-2, which has been characterized previously [Chantret, Rodoloswe, Barbat et al. (1994) J. Cell Sci. 107, 213-225; Mahraoui, Rodolosse, Barbat et al. (1994) Biochem. J. 298, 629-633]. Culture of the cells in dialysed serum and hexose-free media, down-regulated the expression of GLUT5, which was below detection within 3-4 days. This effect was reversed by fructose and glucose feeding of the cells. Fructose feeding yielded a 3-fold higher abundance of GLUT5 protein and mRNA as compared with that expressed in glucose-fed cells. Cells fed normal serum exhibited an inverse hierarchy of expression, with glucose being a better inducer than fructose for the expression of GLUT5. The GLUT5 mRNA and protein abundances obtained in fructose-fed cells did not depend on the type of serum. A linear relationship between cyclic AMP (cAMP) levels and GLUT5 mRNA abundance was found in cells fed dialysed serum, whereas in cells fed normal serum, mRNA abundances were not correlated to cAMP levels. These results indicate that glucose and fructose, together with serum-related factors and cAMP, have combined effects on the expression of GLUT5 in Caco-2 cells.

GLUT8 is a facilitative glucose transporter expressed at high levels in the testis. In this study, we analyzed the GLUT8 expression in mouse testis during spermatogenesis by RT-PCR, Western blot and immunohistochemistry methods. Our results show that GLUT8 expression is limited to spermatids and spermatozoa in the testis. Expression begins when round spermatids are formed at postnatal day 24. The expression persists throughout spermiogenesis, and it is also detected in spermatozoa, but it is absent in more immature germ cells, Sertoli cells and interstitial tissue. GLUT8 immunoreactivity is always restricted to the acrosomic system in a manner that matches the acrosome system formation. The GLUT8 expression is mainly associated with the acrosomic membrane in the acrosome, although significant immunoreactivity is also found inside the acrosomic lumen. The specific GLUT8 location suggests that this transporter plays a pivotal role in the fuel supply of spermatozoa, and in the traffic of sugars during the capacitation and fertilization processes.

Nanocellulose is increasingly being investigated as a paradigm of a sustainable nanomaterial, because of its extraordinary physical and chemical properties, together with its renewable nature and worldwide abundance. The rich structural diversity in cellulose materials is represented by different crystalline allomorphs, from which types I and II stand out. While type I is naturally and ubiquitously