Abstract: The subjects of the present invention are to provide a method of screening a compound or a polypeptide which inhibits the activity of AST, or inhibits PAR activation, mucus production promotion, cell proliferation, intracellular calcium influx or EGFR pathway activation due to AST, and further to provide a method of assaying AST in vivo and in biological cells or samples.

Abstract: Provided are vitamin D.sub.3 derivatives expressed by the following general formula [1] ##STR1## [wherein, R.sub.1 and R.sub.2 are each a hydrogen atom, a trialkylsilyl group, an acetyl group, a methoxymethyl group, or a tetrahydropyranyl group; R.sub.3 and R.sub.4 are each a hydrogen atom, a hydroxyl group, an acyloxy group, an alkyloxy group, an alkylthio group or an alkyl group which is optionally substituted; R.sub.5, R.sub.6, R.sub.7 and R.sub.8 are each a hydrogen atom, a hydroxyl group, an alkyl group or an acyloxy group; R.sub.9 is a hydrogen atom, a hydroxyl group, an alkyl group or an alkylthio group; R.sub.10 is a hydrogen atom, an alkyl group or an alkyloxy group; A and B are each a hydrogen atom, a hydroxyl group, or together express a single bond; X and Y express a carbonyl oxygen, or one of them is a hydrogen atom and the other is a hydroxyl group or an acyloxy group; n is an integer of 0 to 2; m is an integer of 0 to 2], and a method for manufacturing the derivatives.