Chloroplasts are the sub cellular location of both soluble and membrane associated homo serine kinases in pea pisum sativum cultivar alaska leaves

Muhitch, M.J.; Wilson, K.G.

Zeitschrift fuer Pflanzenphysiologie 110(1): 39-46


Accession: 004945937

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Pea leaf homoserine kinase was associated with intact chloroplasts, but not with naked thylakoids (broken chloroplasts), on sucrose density gradients; however, when isolated intact chloroplasts were lysed in the presence of a protective medium, both soluble and thylakoid-associated activities were found. The thylakoid-associated homoserine kinase activity exhibited apparent Km values of 1.2 and 4.7 mM for homoserine and ATP, respectively. The inhibition of the thylakoid-associated homoserine kinase activity by added amino acids was similar to that of the soluble pea leaf homoserine kinase with the exception of S-adenosylmethionine which, when present at 7.5 mM, inhibits the soluble enzyme by 92%, but only inhibited the thylakoid-associated enzyme by 57%. The possible relationship between the soluble and thylakoid forms of the enzyme is discussed.