feat: add RNDR4 reaction #380
Description
The reaction RNDR4 converts UDP to dUDP, and is present in other S. cerevisiae models such as iMM904 (http://bigg.ucsd.edu/models/iMM904/reactions/RNDR4) and iND750 (http://bigg.ucsd.edu/models/iND750/reactions/RNDR4).
It is catalyzed by the ribonucleotide reductase (RNR) complex, which binds UDP (doi:10.1073/pnas.0600443103) and is purported to reduce UDP to dUDP in S. cerevisiae (https://res.slu.se/id/publ/60167) as it does in E. coli (doi:10.1016/S0076-6879(78)51032-X) and mammals (doi:10.1242/dmm.050775). Thus, I think it should be added to the model.