POSTHARVEST BIOCHEMISTRY

PLASMA MEMBRANE DEGRADATION ENZYMES
1. Plasma Membrane
  1. Role of plasma membrane during ripening
    1. 70% of total lipids in mammalian cells are phospholipids - acidic phospholipid (minor but have important role)
      1. Monoacidic - has phosphate but no headgroup (carry one -ve charge that link the headgroup)
      2. Phosphatic acid: carry two -ve charges on the phosphate( has phosphate but no headgroup)
      3. phosphatidylinositol(Ptdlns) : one -ve charged phosphate linking an inostol headgroup to lipid backbone
2. Phospholipases
  1. Lipase enzyme that hydrolyses phospholipid molecules
    1. Phospholipase D
      1. a) Phospholipase D(PLD) hydrolysed phosphatidylcholine (PC) into phosphatidic acid (PA) b) Phospholipase C(PLC) hydrolyses phosphatidylinositl diphosphate (PIP) into diacylglycerol(DAG)
        Hexanal- strong PLD inhibitor
        PLD- membrane degrading enzyme and initiates phospholipid degradation
ETHYLENE BIOSYNTHESIS INHIBITION
1. 1-methylcyclopropene (1-MCP)
  1. prevent ethylene action
  2. competitive inhibitor
  3. stronger affinity than that of ethylene
  4. irreversible binding
    1. interferes ethylene action
    2. delays ethylene biosynthesis
2. Silver thiosulfate (STS)
  1. sodium thioshulfate + silver nitrate
  2. prolong the vase life of cut flower
  3. Ag+ ion blocks ethylene receptor site
    1. delays senescence
  4. not commercialized due to
    1. complicated & sensitive with time of exposure
    2. issue with waste management
GENETIC ENGINEERING
1. goal : add one/more new traits that are not already found in an organim
  1. genetically modifed organism
2. process of manually adding new DNA to an organism
3. common techniques used
  1. RNA interface (RNAi)
  2. gene overexpression
  3. anti-sense
4. plant genetic engineering
  1. agrobacterium
  2. gene gun
ETHYLENE BIOSYNTHESIS
1. Pathway of biosynthesis
  1. Amino acid methionine convert to SAM (S-adenosylmethionine) through SAM synthase
    1. SAM convert to ACC (1-aminocyclopropane-1-carboxylic acid) through ACC synthase (ACS)
      1. ACC convert to ethylene through ACC oxidase (ACO)
2. System in Ethylene Biosynthesis
  1. System I ethylene - Autoinhibition of ethylene synthesis.
  2. System II ethylene - Ethylene production increases due to autocatalytic regulation.
ETHYLENE SIGNALLING

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POSTHARVEST BIOCHEMISTRY

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