Evolution and Distribution of C7-Cyclitol Synthases in Prokaryotes and Eukaryotes.
2-Epi-5-epi-valiolone synthase (EEVS), a C7-sugar phosphate cyclase (SPC) homologous to 3-dehydroquinate synthase (DHQS), was discovered during studies of the biosynthesis of the C7N-aminocyclitol family of natural products. EEVS was originally thought to be present only in certain actinomycetes, but analyses of genome sequences showed that it is broadly distributed in both prokaryotes and eukaryotes, including vertebrates. Another SPC, desmethyl-4-deoxygadusol synthase (DDGS), was later discovered as being involved in the biosynthesis of mycosporine-like amino acid sunscreen compounds. Current database annotations are quite unreliable, with many EEVSs reported as DHQS, and most DDGSs reported as EEVS, DHQS, or simply hypothetical proteins. Here, we identify sequence features useful for distinguishing these enzymes, report a crystal structure of a representative DDGS showing the high similarity of the EEVS and DDGS enzymes, identify notable active site differences, and demonstrate the importance of two of these active site residues for catalysis by point mutations. Further, we functionally characterized two representatives of a distinct clade equidistant from known EEVS and known DDGS groups and show them to be authentic EEVSs. Moreover, we document and discuss the distribution of genes that encode EEVS and DDGS in various prokaryotes and eukaryotes, including pathogenic bacteria, plant symbionts, nitrogen-fixing bacteria, myxobacteria, cyanobacteria, fungi, stramenopiles, and animals, suggesting their broad potential biological roles in nature.
Department of Pharmaceutical Sciences, Oregon State University , Corvallis, Oregon 97331-3507, United States.
Andrew R
AR
Osborn
Department of Biochemistry and Biophysics, Oregon State University , Corvallis, Oregon 97331-3507, United States.
Kelsey M
KM
Kean
Department of Pharmaceutical Sciences, Oregon State University , Corvallis, Oregon 97331-3507, United States.
Khaled M
KM
Alseud
Department of Pharmaceutical Sciences, Oregon State University , Corvallis, Oregon 97331-3507, United States.
Khaled H
KH
Almabruk
Department of Pharmaceutical Sciences, Oregon State University , Corvallis, Oregon 97331-3507, United States.
Shumpei
S
Asamizu
Department of Pharmaceutical Sciences, Oregon State University , Corvallis, Oregon 97331-3507, United States.
Janet A
JA
Lee
Department of Biochemistry and Biophysics, Oregon State University , Corvallis, Oregon 97331-3507, United States.
P Andrew
PA
Karplus
Department of Pharmaceutical Sciences, Oregon State University , Corvallis, Oregon 97331-3507, United States.
Taifo
0000-0001-9639-526X
T
Mahmud
D000595:Amino Acid Sequence; D005075:Biological Evolution; D020134:Catalytic Domain; D019295:Computational Biology; D017124:Conserved Sequence; D018360:Crystallography, X-Ray; D054812:Cyclitols / Q000737:chemistry / Q000378:metabolism*; D005057:Eukaryotic Cells; D008025:Ligases / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D010802:Phylogeny; D011387:Prokaryotic Cells; D017386:Sequence Homology, Amino Acid
D054812:Cyclitols; D008025:Ligases