Opening of new natural substance class for applications in medicine and agriculture

For the first time, researchers in the work­ing groups led by Prof. Tobias Gul­der of TU Dres­den and Prof. Tan­ja Gul­der of the Uni­ver­si­ty of Leipzig have suc­ceed­ed in elu­ci­dat­ing the biosyn­thet­ic mech­a­nisms for the pro­duc­tion of the nat­ur­al sub­stance cyanobac­terin, which is pro­duced in small quan­ti­ties in nature by the blue-green alga Scy­tone­ma hof­man­ni. In the process, they also dis­cov­ered a new class of enzymes for build­ing car­bon-car­bon bonds. The (bio)chemists are thus sig­nif­i­cant­ly expand­ing the bio­cat­alyt­ic reper­toire cur­rent­ly known from nature and open­ing up new, more sus­tain­able biotech­no­log­i­cal appli­ca­tion poten­tials in med­i­cine and agri­cul­ture. The results of the col­lab­o­ra­tion have now been pub­lished in the renowned jour­nal Nature Chem­i­cal Biology.

The fact that nature is an excel­lent chemist is demon­strat­ed by the abun­dance of mol­e­cules, the so-called nat­ur­al sub­stances, that it pro­duces biosyn­thet­i­cal­ly. These nat­ur­al sub­stances are also of cen­tral impor­tance to us humans. They are used in many ways in our every­day lives, espe­cial­ly as active ingre­di­ents in med­i­cine and agri­cul­ture. Promi­nent exam­ples are antibi­otics such as peni­cilins iso­lat­ed from molds, the can­cer drug tax­ol from the Pacif­ic yew tree, and pyrethrins found in chrysan­the­mums, which are used to com­bat pest infestations.

Knowl­edge of nature’s con­struc­tion kit is essen­tial for the devel­op­ment and pro­duc­tion of drugs based on nat­ur­al sub­stances. In this con­text, researchers from the work­ing groups led by Prof. Tobias Gul­der (TU Dres­den) and Prof. Tan­ja Gul­der (Uni­ver­si­ty of Leipzig) joint­ly inves­ti­gat­ed the biosyn­the­sis of cyanobac­terin, which is high­ly tox­ic to pho­to­syn­thet­ic organ­isms and is pro­duced in small quan­ti­ties in nature by the blue-green alga Scy­tone­ma hof­man­ni. In their work, the chemists were not only able to elu­ci­date the for­ma­tion of the nat­ur­al sub­stance for the first time, but also dis­cov­ered a nov­el enzy­mat­ic trans­for­ma­tion for the for­ma­tion of car­bon-car­bon bonds.

This work was made pos­si­ble by com­bin­ing mod­ern tools from bioin­for­mat­ics, syn­thet­ic biol­o­gy, enzy­mol­o­gy and (bio)chemical ana­lyt­ics. The focus was on how the cen­tral part of the cyanobac­terin car­bon skele­ton is pro­duced. The puta­tive genes for this were first cloned by the method of “Direct Path­way Cloning” (DiPaC) and acti­vat­ed in the mod­el organ­ism E. coli as a cell fac­to­ry. DiPaC is a new syn­thet­ic biol­o­gy method pre­vi­ous­ly devel­oped in the lab­o­ra­to­ry of Tobias Gul­der, pro­fes­sor of tech­ni­cal bio­chem­istry at TU Dresden.

“DiPaC allows us to trans­fer entire nat­ur­al prod­uct biosyn­the­sis path­ways into recom­bi­nant host sys­tems very quick­ly and in a tar­get­ed man­ner,” Gul­der explains. In the next step, the research team ana­lyzed the essen­tial indi­vid­ual steps of cyanobac­terin biosyn­the­sis by addi­tion­al­ly pro­duc­ing all key enzymes in the host organ­ism E.coli, iso­lat­ing them and then inves­ti­gat­ing the func­tion of each enzyme. In the process, they came across a pre­vi­ous­ly unknown class of enzymes called fura­no­lide syn­thas­es. These are capa­ble of cat­alyz­ing the for­ma­tion of unusu­al car­bon-car­bon bonds. In fur­ther stud­ies of these fura­no­lide syn­thas­es, these enzymes proved to be high­ly effi­cient in vit­ro bio­cat­a­lysts, mak­ing them high­ly attrac­tive for biotech­no­log­i­cal applications.

“Fura­no­lide syn­thas­es have pro­vid­ed us with a mol­e­c­u­lar tool that will allow us to devel­op more envi­ron­men­tal­ly friend­ly meth­ods for the pro­duc­tion of active ingre­di­ents in the future and thus make our con­tri­bu­tion to a more sus­tain­able chemistry.”

- Prof. Tan­ja Gul­der from the Insti­tute of Organ­ic Chem­istry at the Uni­ver­si­ty of Leipzig

Next, the two research teams want to specif­i­cal­ly search for these nov­el bio­cat­a­lysts in oth­er organ­isms as well, and thus find new bioac­tive mem­bers of this nat­ur­al prod­uct class, as well as devel­op a biotech­no­log­i­cal pro­duc­tion and struc­tur­al diver­si­fi­ca­tion of cyanobac­terin. “Our work paves the way for the com­pre­hen­sive devel­op­ment of an excit­ing class of nat­ur­al prod­ucts for appli­ca­tions in med­i­cine and agri­cul­ture,” agree the two scientists.