. 2013 Apr 1;10(6):909–914. doi: 10.4161/rna.24513

Table 1. PRORP enzymes are less catalytically efficient than RNP-based RNase Ps in vitro.

Species	Composition	k_{_cat} (sec^{^-1})	K_{_m} (nM)	k_{_cat}/K_{_m} (M^{^-1} sec^{^-1})	Fold (k_{_cat}/K_{_m})
B. subtilis^a	RNP	1	230	4 × 10^⁶	40
Nuclear S. cerevisiae^b	RNP	2	20	1 × 10^⁸	1,000
Mito/Chloro A. thaliana PRORP1^c	Protein	0.1	850	1 × 10^⁵	1

A comparison of the catalytic efficiencies (k_cat/K_m) for RNase P enzymes that have been kinetically characterized reveal that PRORP enzymes may be up to several orders of magnitude less efficient. Values reported are from reactions performed at 37°C in the pH range of 7.8–8.0 with respective species specific pre-tRNAs containing 35 nt:CCA, 12 nt:0 nt and 5 nt:1 nt leader to trailer ratios for B. subtilis, S. cerevisiae and A. thaliana, respectively. Reactions performed with RNP-based RNase P contain higher concentrations of magnesium in order to correctly fold and stabilize the large catalytic RNA. ^a(24) ^b(22) ^c [Unpublished results which are comparable to PRORP3 kinetic parameters in (9)] Numbers reported are rounded.