Category I solution for the blocked reaction ADPMAN. ADP-mannose (boxed in red) is a root no-production metabolite within RECON 1. The SMILEY solution (green arrow) involved reversal of the blocked reaction ADPMAN (red arrow). This appears plausible as an enzyme catalysing such a reaction (EC 220.127.116.11) has been described in various mammals  along with the finding that mannose-1-phosphate guanylyltransferase (EC 18.104.22.168) is known to be reversible and accept sugar donors other than GTP .
Rolfsson et al. BMC Systems Biology 2011 5:155 doi:10.1186/1752-0509-5-155