Homogenates of onion seedlings catalyse the decomposition of S-methylmethionine into dimethyl sulphide and homoserine. The reaction is rather slow and seems not to be of primary importance in onion flavour formation or Smethylmethionine metabolism. Extracts of scarlet runner bean seedlings are also active, whereas dormant onion bulb and other seedlings tested showed no or very low activity.

The autolytic enzymic degradation of the muscle of Baltic herring (Clupeu hareugus membrus) was studied by investigating the muscle fractions after two different types of storage corrimonly used in fish handling, i.e. freezing and storage at -3 0 T , and storage at +5"C, comparing them with the muscle fractions of fresh fish. Nuclear, mitochondrial, lysosomal and microsomal as well as soluble fractions were studied by assaying the activities of lysosomal cathepsin D and mitochondrial cytochrome c oxidase. The rnorphology of sedimented fractions as revealed by electron microscopy compared with the enzymic results. After storage, the marker enzymes were detected in the more s!owly sedimenting fractions. Freezing and thawing also resulted in the lysis of mitochondria and lysosomes and in a loose, disorganised muscle structure.

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