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Edited by Sandro SonninoKeywords: IgG-opsonized red blood cell Phagosome maturation Phosphoinositide 3 0 -phosphatase PTEN PIKfyve RAW264.7 macrophage a b s t r a c t PtdIns(3)P (phosphatidylinositol 3-phosphate) is a signaling molecule important for phagosome maturation. The major role of Vps34 in production of phagosomal PtdIns(3)P has been indicated. However, the fate of the newly generated PtdIns(3)P has not been well described. Here we show that elimination of PtdIns(3)P from phagosomal membrane was significantly delayed in RAW264.7 macrophages lacking PTEN or PIKfyve. In the PTEN-deficient cells treated with a PIKfyve inhibitor, degradation of PtdIns(3)P was almost lost, indicating that PTEN and PIKfyve are two major players in phagosomal PtdIns(3)P metabolism.

A comparison was made of the deamidation activity of transglutaminases from guinea pig liver (GTGase), fish red sea bream liver (FTGase) and microorganisms (MTGase). Against the Z-Gln-Gly, kinetic constants of the deamidation and incorporation of primary amine were measured. GTGase and FTGase showed similar deamidation activity, however, that of MTGase was less than 1/7 of the other two TGases. Against the proteins, N, N-dimethylated casein and native gliadin, FTGase was the most active and deamidated respectively 45.5% and 38.2% of Gln residues. The deamidation rate of these proteins by GTGase was less than 1/2 and these results were expected to be caused by the difference of substrate specificity of the TGases.