>gnl|CDD|176187 cd05284, arabinose_DH_like, D-arabinose dehydrogenase. This group contains arabinose dehydrogenase (AraDH) and related alcohol dehydrogenases. AraDH is a member of the medium chain dehydrogenase/reductase family and catalyzes the NAD(P)-dependent oxidation of D-arabinose and other pentoses, the initial step in the metabolism of d-arabinose into 2-oxoglutarate. Like the alcohol dehydrogenases, AraDH binds a zinc in the catalytic cleft as well as a distal structural zinc. AraDH forms homotetramers as a dimer of dimers. AraDH replaces a conserved catalytic His with replace with Arg, compared to the canonical ADH site. NAD(P)(H)-dependent oxidoreductases are the major enzymes in the interconversion of alcohols and aldehydes, or ketones. Alcohol dehydrogenase in the liver converts ethanol and NAD+ to acetaldehyde and NADH, while in yeast and some other microorganisms ADH catalyzes the conversion acetaldehyde to ethanol in alcoholic fermentation. ADH is a member of the medium chain alcohol dehydrogenase family (MDR), which has a NAD(P)(H)-binding domain in a Rossmann fold of a beta-alpha form. The NAD(H)-binding region is comprised of 2 structurally similar halves, each of which contacts a mononucleotide. A GxGxxG motif after the first mononucleotide contact half allows the close contact of the coenzyme with the ADH backbone. The N-terminal catalytic domain has a distant homology to GroES. These proteins typically form dimers (typically higher plants, mammals) or tetramers (yeast, bacteria), and have 2 tightly bound zinc atoms per subunit, a catalytic zinc at the active site and a structural zinc in a lobe of the catalytic domain. NAD(H) binding occurs in the cleft between the catalytic and coenzyme-binding domains at the active site, and coenzyme binding induces a conformational closing of this cleft. Coenzyme binding typically precedes and contributes to substrate binding. In human ADH catalysis, the zinc ion helps coordinate the alcohol, followed by deprotonation of a histidine, the ribose of NAD, a serine, then the alcohol, which allows the transfer of a hydride to NAD+, creating NADH and a zinc-bound aldehyde or ketone. In yeast and some bacteria, the active site zinc binds an aldehyde, polarizing it, and leading to the reverse reaction. Length = 340

 Score =  109 bits (275), Expect = 1e-24
 Identities = 80/301 (26%), Positives = 135/301 (44%), Gaps = 51/301 (16%)

Query: 7   MRHVAMSGYGKSNVMFLAESPIPQPQKEEILIKVEAIGVNRPDVMQRKGLYPPPKNANP- 65
           M+   +  YGK   + L + P+P+P   ++L++V   GV   D+    G         P 
Sbjct: 1   MKAARLYEYGKP--LRLEDVPVPEPGPGQVLVRVGGAGVCHSDLHVIDG---VWGGILPY 55

Query: 66  ----ILGLEVAGKIVDLGENTTHWNIGDEVCALVNG------------------------ 97
                LG E AG + ++G        GD V  +V+                         
Sbjct: 56  KLPFTLGHENAGWVEEVGSGVDGLKEGDPV--VVHPPWGCGTCRYCRRGEENYCENARFP 113

Query: 98  -----GGYAEYCLSHQGHTLPIPKGYNAIQAASLPESFFTVWANLFQTAN-LRSGQTVLI 151
                GG+AEY L      + +P+G + ++AA L ++  T +  + +    L  G TV++
Sbjct: 114 GIGTDGGFAEYLLVPSRRLVKLPRGLDPVEAAPLADAGLTAYHAVKKALPYLDPGSTVVV 173

Query: 152 HG-GSSGIGTTAIQLASYF-GATVYTTAKSEEKCLACLKLGAKHAINYLKEDFLEILQKE 209
            G G  G+G  A+Q+      ATV    +SEE      +LGA H +N   +D +E +++ 
Sbjct: 174 IGVG--GLGHIAVQILRALTPATVIAVDRSEEALKLAERLGADHVLN-ASDDVVEEVREL 230

Query: 210 TQGRGIDIILDMVGA-EYLNQHLTLLSKEGKLIIISFLGGNIATEINLNPIISKRITITG 268
           T GRG D ++D VG+ E L     LL+K G+ +I+   GG+    +  + ++   I++ G
Sbjct: 231 TGGRGADAVIDFVGSDETLALAAKLLAKGGRYVIVG-YGGHG--RLPTSDLVPTEISVIG 287

Query: 269 S 269
           S
Sbjct: 288 S 288