| Popis: |
Summary Sucrose density gradient centrifugation of homogenates from dormant or differentiating potato tuber tissue ( Solanum tuberosum L. cv. Bintje ) showed an increase during differentiation of peroxisomes (s. d. 1.25-1.26), mitochondria (s. d. 1.19-1.20) and acid phosphatase-containing membrane fractions (s.d. 1.18-1.24). The organelles were identified by markerenzyme distribution and by electronmicroscopy of the pooled fractions. None of the dehydrogenases tested was found associated with the peroxisomes or the particulate acid phosphatase fractions. In addition, no specific electroforetic separable band of MDH was detected in peroxisomal fractions. The location in the mitochondria was highest for MDH and GDH (10-37 0/o of the total activity), while NAD-GAPDH/PGK was less mitochondrial-bound (2-14 0/o of the total activity). LDH, malic enzyme, ADH and NADP-GAPDH/PGK could hardly or not be detected in mitochondrial fractions (0-2 0/o of the total activity). The NADP-dependent activities of GDH, ADH and GAPDH/PGK increased more than 200 0/o in the tissue during differentiation. The other enzyme activities increased less or remained stable, except NADP-ADH that decreased after wounding. The use of LDH and malic enzyme for the determination of free redox ratios of NAD and NADP respectively in the cytoplasm of potato tuber tissue is recommended. |
