>gnl|CDD|176213 cd08251, polyketide_synthase, polyketide synthase. Polyketide synthases produce polyketides in step by step mechanism that is similar to fatty acid synthesis. Enoyl reductase reduces a double to single bond. Erythromycin is one example of a polyketide generated by 3 complex enzymes (megasynthases). 2-enoyl thioester reductase (ETR) catalyzes the NADPH-dependent dependent conversion of trans-2-enoyl acyl carrier protein/coenzyme A (ACP/CoA) to acyl-(ACP/CoA) in fatty acid synthesis. 2-enoyl thioester reductase activity has been linked in Candida tropicalis as essential in maintaining mitiochondrial respiratory function. This ETR family is a part of the medium chain dehydrogenase/reductase family, but lack the zinc coordination sites characteristic of the alcohol dehydrogenases in this family. 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 have 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. 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. Length = 303

 Score =  156 bits (397), Expect = 6e-39
 Identities = 92/308 (29%), Positives = 156/308 (50%), Gaps = 11/308 (3%)

Query: 28  IPQPQKEEILIKVEAIGVNRPDVMQRKGLYP--PPKNANPILGLEVAGKIVDLGENTTHW 85
           +  P   E+ I+V A  +N  D++  +GLYP  PP    P  G E +G +  +G + T  
Sbjct: 2   VAPPGPGEVRIQVRAFSLNFGDLLCVRGLYPTMPPYPFTP--GFEASGVVRAVGPHVTRL 59

Query: 86  NIGDEVCALVNG--GGYAEYCLSHQGHTLPIPKGYNAIQAASLPESFFTVWANLFQTANL 143
            +GDEV A      GG+A      +   +  P   +  +A +LP  F TV  + F  A L
Sbjct: 60  AVGDEVIAGTGESMGGHATLVTVPEDQVVRKPASLSFEEACALPVVFLTVI-DAFARAGL 118

Query: 144 RSGQTVLIHGGSSGIGTTAIQLASYFGATVYTTAKSEEKCLACLK-LGAKHAINYLKEDF 202
             G+ +LI   + G G  A+QLA   GA +Y TA S++K L  LK LG  H INY++EDF
Sbjct: 119 AKGEHILIQTATGGTGLMAVQLARLKGAEIYATASSDDK-LEYLKQLGVPHVINYVEEDF 177

Query: 203 LEILQKETQGRGIDIILDMVGAEYLNQHLTLLSKEGKLIIISFLGGNIATEINLNPIISK 262
            E + + T GRG+D++++ +  E + + L  L+  G+ + I+      A  ++L+ ++S 
Sbjct: 178 EEEIMRLTGGRGVDVVINTLSGEAIQKGLNCLAPGGRYVEIAMTALKSAPSVDLS-VLSN 236

Query: 263 RITITGSTLRRRTDIAKQSIRDSLQLKIWPLLNSHVIAPVIHTVLPLGKVAMAHDIMEKS 322
             +     LR+   +  + I D  Q ++  L+    + P +  + P   +  A+  +   
Sbjct: 237 NQSFHSVDLRKLLLLDPEFIAD-YQAEMVSLVEEGELRPTVSRIFPFDDIGEAYRYLSDR 295

Query: 323 EHIGKIIL 330
           E+IGK+++
Sbjct: 296 ENIGKVVV 303