A Critical Tryptophan and Ca2+ in Activation and Catalysis of TPPI, the Enzyme Deficient in Classic Late-Infantile Neuronal Ceroid Lipofuscinosis

Tripeptidyl aminopeptidase I (TPPI) is a crucial lysosomal enzyme that is deficient in the fatal neurodegenerative disorder called classic late-infantile neuronal ceroid lipofuscinosis (LINCL). It is involved in the catabolism of proteins in the lysosomes. Recent X-ray crystallographic studies have provided insights into the structural/functional aspects of TPPI catalysis, and indicated presence of an octahedrally coordinated Ca(2+).Purified precursor and mature TPPI were used to study inhibition by NBS and EDTA using biochemical and immunological approaches. Site-directed mutagenesis with confocal imaging technique identified a critical W residue in TPPI activity, and the processing of precursor into mature enzyme.NBS is a potent inhibitor of the purified TPPI. In mammalian TPPI, W542 is critical for tripeptidyl peptidase activity as well as autocatalysis. Transfection studies have indicated that mutants of the TPPI that harbor residues other than W at position 542 have delayed processing, and are retained in the ER rather than transported to lysosomes. EDTA inhibits the autocatalytic processing of the precursor TPPI.We propose that W542 and Ca(2+) are critical for maintaining the proper tertiary structure of the precursor proprotein as well as the mature TPPI. Additionally, Ca(2+) is necessary for the autocatalytic processing of the precursor protein into the mature TPPI. We have identified NBS as a potent TPPI inhibitor, which led in delineating a critical role for W542 residue. Studies with such compounds will prove valuable in identifying the critical residues in the TPPI catalysis and its structure-function analysis

Heliozoa from Nigeria

A total of seven scaled protistans were observed from four freshwater sites in Nigeria. They include the holiozoan genera Acanthocystis, Polyplacocystis, Pterocystis, and Raphidiophrys. All are new records for Africa. KEY WORDS: Heliozoa, Protozoa, Acanthocystis, Polyplacocystis, Pterocystis, Raphidiophrys Tropical Freshwater Biology 11 (2002) 1-

Silica-scaled chrysophyceae and synurophyceae (chrysophyta) from Nigeria. II. Lake Lekki

A total of 20 silica-scaled chrysophytes (Chrysophyceae: two Paraphysomonas spp. and one Spiniferomonas sp.; Synurophyceae: 10 Mallomonas spp. and seven Synura spp.) was recorded from samples collected from Lekki Lagoon, Nigeria, over a period of 12 months in 2003-2004 based on transmission and scanning electron microscopy. Included is a description of a new species of Paraphysomonas, P. nigeriensis. Fifteen are new records for the country. Keywords: silica-scaled chrysophytes, Mallomonas, Paraphysomonas, Spiniferomonas, Synura Tropical Freshwater Biology 2003/2004 Vol. 12/13: 99-10

Description of a new freshwater species of Thaumatomastix (Protista, Thaumatomonadida) from Nigeria, West Africa

Thaumatomastix (Protista, Thaumatomonadida) is a free swimming heterotrophic genus sporadically reported from both marine and freshwater habitats. The genus at present comprises fourteen species none of which have been reported from Africa. We describe a new freshwater species from Nigeria, Thaumatomastix nigeriensis, using TEM