Reaction Network

digraph Reactions {
  rankdir=LR;
  node [shape=box, style="rounded,filled", fillcolor="#fee2e2"];
  A -> B [label="k1"];
  B -> C [label="k2"];
  C -> D [label="k3"];
  B -> E [label="k4"];
  E -> D [label="k5"];
  D -> A [label="k-1", color="#94a3b8"];
}