胆固醇代谢过程

Fig.2.Proposedpathwayforcholesteroldegradationunderaerobicconditions.Cholest-4-en-3-oneoranyofthesubsequent

metabolitesfromdegradationoftheside-chainupto(andincluding)ADmayundergoadehydrogenationreactiontointroduce

adoublebondintheposition1,leadingtocompoundcholest-1,4-diene-3-oneinthecaseofcholest-4-en-3-one,ortothe

corresponding1,2-dehydroderivativesforothermolecules.Theside-chaindegradationofthiscompoundswillbeidenticalto

thatofthecholest-4-en-3-onetothecommonintermediate9a-hydroxyandrosta-1,4-diene-3,17-dione.Themicroorganisms

fromwhichenzymesimplicatedindifferentstepsareindicatedbynumbers.Numbersinbracketsareassignedarbitrarilyto

facilitatethecompoundidentificationin

Fig.3.Proposedb-oxidation-likereactionsforcholesterolside-chaindegradation.TheFadproteinshavebeenassigned

accordingtothenomenclatureoftheE.colgienesinvolvedintheb-oxidationoffattyacids.LiuEisthenameassignedto

3-hydroxy-3-methylglutaryl-coenzymelyases.

Fig.4.OrganizationofthemaingeneclustersimpliedorsuggestedtobeinvolvedinthedegradationofcholesterolinM.

smegmatismc2155.TheidentitynumberforeachMSMEGgeneisindicatedwithinthearrows.Thenameofsomegenesof

interestiswrittenabovethem.

Numbersbelowgenesindicatethenumberofbpbetweenadjacentgenes;numbersinbracketsindicateseparationand

numbersinparenthesesindicateoverlap.

Numbersabovediagonallinesindicatethegenomicpositioninkb.

Orange:mcecluster.Green:genessuggestedand/orprovedtoparticipateintheside-chaindegradation.Blue:genes

suggestedand/orprovedtoparticipateinthecentralorlowercatabolicpathway.

Yellow:genescodingthetranscriptionalrepressorsKstRandKstR2.

GenessurroundedbyadashedlinearecontrolledbyKstR2,therestofthegenesshowedinthisfigurearecontrolledbyKstR

(exceptforMSMEG_5905,5909,5910,5912,5916,5917,5924,5926,5928,5936,5938,60