Evolutionary constraints on the effectiveness of enzymatic function result in well-defined architectures of active sites. In this study we show that these constraints are fully pronounced even at the backbone level. We explore the possibility of defining catalytic triads in proteases just by their relative backbone orientations to dramatically speed up the scaffold search problem of de novo enzyme design. An order of magnitude speed-up achieved this way paves a way to a routine scanning of the whole structural proteome including modeled structures.