Amino-Acid Homopolymers Occurring in Nature

173 Pages·2010·3.02 MB·English

by  Munenori Takehara

Microbiology Monographs
Volume 15
Series Editor: Alexander Steinbu¨chel
Mu¨nster,Germany
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Yoshimitsu Hamano
Editor
Amino-Acid Homopolymers
Occurring in Nature
Editor
YoshimitsuHamano,Ph.D.
DepartmentofBioscience
FukuiPrefecturalUniversity
4-1-1Matsuoka-Kenjojima,Eiheiji-cho
Fukui910-1195
Japan
[email protected]
SeriesEditor
ProfessorDr.AlexanderSteinbu¨chel
Institutfu¨rMolekulareMikrobiologieundBiotechnology
Westfa¨lischeWilhelms-Universita¨t
Corrensstr.3
48149Mu¨nster
Germany
[email protected]
ISSN1862-5576 e-ISSN1862-5584
ISBN978-3-642-12452-5 e-ISBN978-3-642-12453-2
DOI10.1007/978-3-642-12453-2
SpringerHeidelbergDordrechtLondonNewYork
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#Springer-VerlagBerlinHeidelberg2010
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Preface
Biopolymersarethemostabundantmoleculesinlivingmatter.Microorganismsare
capable of producing a wide variety of biopolymers, including polynucleotides,
polyamides(protein),polysaccharides,polyphosphate,polyesters,andpolyketides.
However,homopolymers,whicharemadeupofonlyasingletypeofaminoacid,
are far less ubiquitous; in fact, only two amino-acid homopolymers are known to
occur in nature: poly-e-L-lysine (e-poly-L-lysine, e-PL) and g-poly-glutamic acid
(g-PGA).
e-PL,consistingof25–30L-lysineresidueswithalinkagebetweenthea-carboxyl
group and the e-amino group, is produced by actinomycetes. Because e-PL is a
polycationicpeptideandthusexhibitsantimicrobialactivityagainstawidespectrum
of microorganisms, including Gram-positive and Gram-negative bacteria, and
because it is both safe and biodegradable, e-PL is used as a food preservative in
several countries. In contrast, g-PGA is an unusual anionic polypeptide in which
D-and/orL-glutamateispolymerizedviag-amidelinkages.g-PGAissecretedintothe
growthmediumofBacillussubtilisasafermentationproductwithavariablemolecu-
larweight(typically,10–1,000kDa).
Overthepastdecade,thebiologicalandchemicalfunctionsofthesetwohomo-
polyaminoacidshavebeenreported,therebybeingpromisingmaterialsformedi-
calandindustrialapplications.ThisMicrobiologyMonographsvolumecoversthe
current knowledge and most recent advances in regard to the occurrence, biosyn-
thetic mechanisms, biodegradations, and industrial and medical applications of
thesepolymers.
Fukui,Japan YoshimitsuHamano
v
Contents
OccurrenceandProductionofPoly-Epsilon-L-Lysine
inMicroorganisms ............................................................. 1
MunenoriTakeharaandHideoHirohara
BiochemistryandEnzymologyofPoly-Epsilon-L-Lysine
Biosynthesis .................................................................... 23
YoshimitsuHamano
BiochemistryandEnzymologyofPoly-Epsilon-L-Lysine
Degradation .................................................................... 45
ToyokazuYoshida
BiotechnologicalProductionofPoly-Epsilon-L-LysineforFood
andMedicalApplications ..................................................... 61
KazuyaYamanakaandYoshimitsuHamano
OccurrenceandBiosyntheticMechanism
ofPoly-Gamma-GlutamicAcid .............................................. 77
MakotoAshiuchi
EnzymaticDegradationofPoly-Gamma-GlutamicAcid .................. 95
KeitarouKimuraandZuiFujimoto
PharmaceuticalandMedicalApplications
ofPoly-Gamma-GlutamicAcid ............................................. 119
TakamiAkagi,MichiyaMatsusaki,andMitsuruAkashi
FoodApplicationsofPoly-Gamma-GlutamicAcid ........................ 155
HiroyukiTanimoto
Index ........................................................................... 169
vii
Occurrence and Production of
Poly-Epsilon- -Lysine in Microorganisms
L
MunenoriTakeharaandHideoHirohara
Contents
1 Introduction ..................................................................................2
2 ScreeningandDiscoveryofPoly-e-L-LysinePolymers......................................3
2.1 FirstDiscoveryasDragendorff-PositiveSubstance....................................4
2.2 EveryProducerStrainHase-PL-DegradingActivity ..................................4
2.3 HighThroughputScreeninginAgarPlates ............................................5
2.4 FrequentOccurrencesFoundbyTwo-StageCultureMethod..........................5
3 ProductionBehaviorinStreptomycesStrains ................................................6
3.1 FeaturesShownbytheTwoStrains ...................................................7
3.2 EffectsoftheCultureMedium.........................................................8
3.3 ReleaseofPolymersintotheCultureBroth ...........................................9
3.4 Developmentofe-PL-HydrolyzingActivity ......................................... 10
4 PolymerStructureofe-PLinStreptomycesStrains ........................................ 12
5 TwoAdvantageousProducers ............................................................. 14
5.1 StreptomyceslydicusUSE-11 ........................................................ 14
5.2 StreptomycesaureofaciensUSE-82.................................................. 14
6 ProductionControlandChainLengthShortening ......................................... 15
6.1 CellDensity-DependentProduction ................................................. 15
6.2 ChainLengthShorteningbyAliphaticHydroxy-compounds ........................ 16
6.3 ChainLengthShorteningAssistedbySulfatedb-Cyclodextrin ..................... 17
7 Poly(AminoAcid)Coproducedwithe-PL ................................................. 18
7.1 Poly-g-L-DiaminobutanoicAcid ..................................................... 18
7.2 Lariat-ShapedPoly-g-L-GlutamicAcid .............................................. 19
8 ConcludingRemarks....................................................................... 20
References ......................................................................................21
M.Takehara(*)
Department of Materials Science, University of Shiga Prefecture, 2500 Hassaka, Hikone
522-8533,Japan
e-mail:[email protected]
H.Hirohara(*)
Department of Materials Science, University of Shiga Prefecture, 2500 Hassaka, Hikone 522-
8533,Japan
MEALaboratory,4-31-18Takakuradai,Minami-ku,Sakai590-0117,Japan
e-mail:[email protected]
Y.Hamano(ed.),Amino-AcidHomopolymersOccurringinNature, 1
MicrobiologyMonographs15,DOI10.1007/978-3-642-12453-2_1,
#Springer-VerlagBerlinHeidelberg2010
2 M.TakeharaandH.Hirohara
Abstract This chapter addresses the occurrence and production of poly-e-L-lysine
(e-PL) in filamentous bacteria from the family Streptomycetaceae and ergot fungi,
especiallyinthegenusStreptomyces.Thepresenceofe-PL,firstdiscoveredfroma
strainamong 2,000 actinomycetes, was found quite frequentlyin various strains of
Streptomyces by novel screening methods, including the two-stage culture of cell
growth and e-PL production cultures. Using the newly isolated producer strains of
Streptomyces,theirproductionbehaviorswerestudiednotonlyintermsofthetime
courseof several production factors and effect ofculture medium components, but
alsootheraspectsofthereleaseofsynthesizede-PLintotheculturebrothandofthe
simultaneous development of e-PL hydrolase activity with the e-PL-producing
machinery. The e-PLs obtained were evaluated structurally. The results revealed
thatthepolymershadanearlymonodispersedstructure,andcouldbeclassifiedinto
five groups based on their chain lengths. The cell density-dependent control of the
productionofe-PL,thechainlengthshorteningbyaliphatichydroxy-compounds,and
thecoproductionofnovelaminoacidhomopolymerswithe-PLarealsodiscussed.
1 Introduction
Poly-e-L-lysine(e-PL)(alsocallede-poly-L-lysine)isanL-lysinelinearhomopoly-
mer biosynthesized extracellularly, and has a unique structure linking e-amino
and a-carboxylic acid functional groups (Fig. 1). The polymer of 25–35 residues
wasdiscoveredasasecretedproductfromastrainofStreptomycesalbulusNo.346,
now designated S. albulus NBRC 14147 (NBRC 14147), in culture filtrates
(Shima and Sakai 1977). The compound is biodegradable and water soluble, and
has various functions such as antimicrobial activity (Shima et al. 1984; Hiraki
2000), antiphage action (Shima et al. 1982), endotoxin-selective removal action
(Hirayama et al. 1999), and antiobesity action due to the inhibition of pancreatic
lipase(Tsujitaetal.2006).Thispolymerispracticallynontoxicinacute,subchro-
nic and chronic feeding studies in rats, and nonmutagenic in bacterial reversion
assays(Hirakietal.2003).SincethediscoveryofNBRC14147,theproductionof
e-PL has been enhancednearly 100-foldthroughvariousoptimization attemptsin
fermentationtechniquessuchasstrictcontrolsofthepHandglucoseconcentration
ofculturemediausingacertainmutantofthefirststrain(Kaharetal.2001).e-PL
is manufactured at the commercial scale by a fermentation process using the
mutant of NBRC 14147, and is used as a food preservative in several countries
(Oppermann-SanioandSteinb€uchel2002;YoshidaandNagasawa2003).
Despitethefactthatthispolymerwasscientificallysointerestingandpractically
souseful,studiesone-PLhavebeenratherlimitedbothinquantity,scopeandthe
O
H d b
Fig.1 Chemicalstructureof N a
e-poly-L-lysine(e-PL)
e g
biosynthesizedin NH +
microorganisms 3 n
OccurrenceandProductionofPoly-Epsilon-L-LysineinMicroorganisms 3
level of detail examined as compared with poly-g-glutamic acid (g-PGA) (see
chapter “Occurrence and Biosynthetic Mechanism of Poly-Gamma-Glutamic
Acid” by Ashiuchi) or cyanophycin, the storage amino acid polymer which accu-
mulates inside producing cells (Oppermann-Sanio and Steinb€uchel 2002, 2003).
Thismightbemainlyattributedtothefactthateversincethefirstdiscoveryofthe
S. albulus strain, no microorganisms producing e-PL had been isolated until
recently when two novel screening methods succeeded inisolating several strains
of Streptomycetaceae and ergot fungi (Nishikawa and Ogawa 2002; Kito et al.
2002a). All of the specific properties mentioned above were studied using e-PL
samples fromNBRC 14147 or its mutant. g-PGAwas discovered40 years before
e-PL(Iva´novicsandErdo¨s1937),andmanyexperimentshavebeenperformedonit
over the years in various fields and levels. Cyanophycin, discovered in the nine-
teenth century, has also been well studied in terms of its biosynthesis at the
molecularandbiologicallevels(Oppermann-SanioandSteinb€uchel2002,2003).
Under these circumstances, the presence of e-PL was found to be much more
frequentthanhadbeenanticipated,throughthescreeningofvariousactinomycete
strains (Hirohara et al. 2007). Of the plus 200 strains found to produce cationic
polymers,tenstrainsandtheire-PLswerestudiedindetail.Alltenbelongedtothe
genus Streptomyces. The authors examined the effects of the components of the
culture medium on e-PL production as well as the production behaviors in these
strains (Hirohara et al. 2006). They reported the number of lysine residues (R ),
n
number and weight average molecular weight (M , M ), and polydispersity index
n w
(M /M )ofthepolymersobtainedfromglycerolorglucose(Hiroharaetal.2007).
w n
They also studied how the e-PL was released into the culture broth, and how the
development of e-PL-production and hydrolyzing activities were correlated in
certain producer strains (Saimura et al. 2008). All of these reports will further
facilitatethestudyofe-PLinbothfundamentalresearchandtechnicalapplications
byobtainingavarietyofnovelpolymerswithdesirablepolymericstructures.
Thischaptergivesanup-to-dateoverviewontheoccurrenceandproductionof
e-PLinmicroorganisms.Itincludesthefrequentoccurrenceofe-PLswithvarious
R s, the nearly monodispersed structures of e-PLs irrespective of their R s, the
n n
controlofproduction,shorteningofthechainlengththroughesterification,andthe
coproduction of another amino-acid homopolymer (poly(amino acid)) with e-PL.
The biosynthetic mechanism is not discussed here, since the genes and enzymes
involved in the biosynthesis are discussed fully in chapter “Biochemistry and
EnzymologyofPoly-Epsilon-L-LysineBiosynthesis”byHamano.
2 Screening and Discovery of Poly-«-L-Lysine Polymers
A quarter of a century after the discovery of the first producer strain, a dozen
microorganisms have been found to produce the polymer using two novel and
independent screening methods. Thereafter, the much more frequent presence of
e-PLthanhadbeenpreviouslyanticipatedwassupportedbyscreeningsofvarious