BIOSYNTHESIS OF LIGNIN

Course teacher :- Dr.uma ProfessorDr . Govindraju professor

Presented by :- Kale Ravindra

Ramrao

09-607-05

INTRODUCTION• Lignin is a cross-linked phenolic polymer that interferes with

the degradation of plant cell walls.

• It find in vascular tissues cell wall as well as in cell walls of pith, root, fruit

.• Not uniformly distributed in call wall

• Protect microfibrils from chemical, physical , and biological attack.

• give hydroxycinnamyl alcohols or "monolignols", the monomeric precursors of lignin .

• Strengthens the cell wall

Enzymes involved in lignin biosynthesis

• cinnamyl-alcohol dehydrogenase (CAD)• phenylalanine ammonia-lyase(PAL)• caffeoyl-CoA 3-O-methyltransferase

(CCOMT)• Cinnamate 4-hydroxylase (C₄H)• 4-coumarate CoA –ligase(4CL)• Ferulate-5-hydroxylase(F5H)• Cinnayml-coA reductase(CCR)

• Oxidation of lignin with nitrobenzene in alkaline medium to find structure of lignin

• Gymnosperm lignin = vanillin + p-hydroxy benzaldihyde

• Dicot lignin = vanillin + syringaldehyde

• Monocot lignin = all three components

In vitro synthesis of lignin like polymer

• Done by Fruedenerg in 1950 by using phenol oxidase enzyme which later on identified as laccase.

• Laccase carry out conversation of coniferyl alcohol to lignin like polymer.

• These were isolated and their structure determined.

• Polymerization process involved the random non-enzymatic reaction of free radicals.

• Licot lignin is formed from coniferyl alcohols and sinapyl alcohols.

• Monocot lignin is formed from coniferyl, sinapyl and p-coumaryl alcohol

• Symplastic cinnamylalochol glucosyltransferase storage (vacuole)

transportase apoplastic

cinnamyl glucosidesApoplastic cinnamyl alcohol β-glucosidase

lignin

Storage , transportation , and degeneration of Monolignol glucosids

DISCUSSION

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